v2/README: make a definitive decision on v2 import path

This change makes it clear that the v2 import path
is github.com/russross/blackfriday/v2, and updates
various links accordingly.

See #587 (comment) for details.

This change also converges the README for v1 and v2
to be consistent, as they've started to drift apart.

For #587.

GitHub-Pull-Request: #675

README.md

@@ -1,4 +1,6 @@
-Blackfriday [![Build Status](https://travis-ci.org/russross/blackfriday.svg?branch=master)](https://travis-ci.org/russross/blackfriday)
+Blackfriday
+[![Build Status][BuildV2SVG]][BuildV2URL]
+[![PkgGoDev][PkgGoDevV2SVG]][PkgGoDevV2URL]
 ===========
 
 Blackfriday is a [Markdown][1] processor implemented in [Go][2]. It
@@ -16,33 +18,31 @@ It started as a translation from C of [Sundown][3].
 Installation
 ------------
 
-Blackfriday is compatible with any modern Go release. With Go 1.7 and git
-installed:
+Blackfriday is compatible with modern Go releases in module mode.
+With Go installed:
 
-    go get gopkg.in/russross/blackfriday.v2
+    go get github.com/russross/blackfriday/v2
 
-will download, compile, and install the package into your `$GOPATH`
-directory hierarchy. Alternatively, you can achieve the same if you
-import it into a project:
+will resolve and add the package to the current development module,
+then build and install it. Alternatively, you can achieve the same
+if you import it in a package:
 
-    import "gopkg.in/russross/blackfriday.v2"
+    import "github.com/russross/blackfriday/v2"
 
 and `go get` without parameters.
 
+Legacy GOPATH mode is unsupported.
+
 
 Versions
 --------
 
 Currently maintained and recommended version of Blackfriday is `v2`. It's being
 developed on its own branch: https://github.com/russross/blackfriday/tree/v2 and the
 documentation is available at
-https://godoc.org/gopkg.in/russross/blackfriday.v2.
+https://pkg.go.dev/github.com/russross/blackfriday/v2.
 
-It is `go get`-able via via [gopkg.in][6] at `gopkg.in/russross/blackfriday.v2`,
-but we highly recommend using package management tool like [dep][7] or
-[Glide][8] and make use of semantic versioning. With package management you
-should import `github.com/russross/blackfriday` and specify that you're using
-version 2.0.0.
+It is `go get`-able in module mode at `github.com/russross/blackfriday/v2`.
 
 Version 2 offers a number of improvements over v1:
 
@@ -62,6 +62,11 @@ Potential drawbacks:
   v2. See issue [#348](https://github.com/russross/blackfriday/issues/348) for
   tracking.
 
+If you are still interested in the legacy `v1`, you can import it from
+`github.com/russross/blackfriday`. Documentation for the legacy v1 can be found
+here: https://pkg.go.dev/github.com/russross/blackfriday.
+
+
 Usage
 -----
 
@@ -91,7 +96,7 @@ Here's an example of simple usage of Blackfriday together with Bluemonday:
 ```go
 import (
     "github.com/microcosm-cc/bluemonday"
-    "github.com/russross/blackfriday"
+    "github.com/russross/blackfriday/v2"
 )
 
 // ...
@@ -116,7 +121,7 @@ markdown file using a standalone program.  You can also browse the
 source directly on github if you are just looking for some example
 code:
 
-* <http://github.com/russross/blackfriday-tool>
+* <https://github.com/russross/blackfriday-tool>
 
 Note that if you have not already done so, installing
 `blackfriday-tool` will be sufficient to download and install
@@ -133,12 +138,12 @@ anchors for headings when `AutoHeadingIDs` extension is enabled. The
 algorithm has a specification, so that other packages can create
 compatible anchor names and links to those anchors.
 
-The specification is located at https://godoc.org/gopkg.in/russross/blackfriday.v2#hdr-Sanitized_Anchor_Names.
+The specification is located at https://pkg.go.dev/github.com/russross/blackfriday/v2#hdr-Sanitized_Anchor_Names.
 
-[`SanitizedAnchorName`](https://godoc.org/gopkg.in/russross/blackfriday.v2#SanitizedAnchorName) exposes this functionality, and can be used to
+[`SanitizedAnchorName`](https://pkg.go.dev/github.com/russross/blackfriday/v2#SanitizedAnchorName) exposes this functionality, and can be used to
 create compatible links to the anchor names generated by blackfriday.
 This algorithm is also implemented in a small standalone package at
-[`github.com/shurcooL/sanitized_anchor_name`](https://godoc.org/github.com/shurcooL/sanitized_anchor_name). It can be useful for clients
+[`github.com/shurcooL/sanitized_anchor_name`](https://pkg.go.dev/github.com/shurcooL/sanitized_anchor_name). It can be useful for clients
 that want a small package and don't need full functionality of blackfriday.
 
 
@@ -217,6 +222,15 @@ implements the following extensions:
     You can use 3 or more backticks to mark the beginning of the
     block, and the same number to mark the end of the block.
 
+    To preserve classes of fenced code blocks while using the bluemonday
+    HTML sanitizer, use the following policy:
+
+    ```go
+    p := bluemonday.UGCPolicy()
+    p.AllowAttrs("class").Matching(regexp.MustCompile("^language-[a-zA-Z0-9]+$")).OnElements("code")
+    html := p.SanitizeBytes(unsafe)
+    ```
+
 *   **Definition lists**. A simple definition list is made of a single-line
     term followed by a colon and the definition for that term.
 
@@ -268,7 +282,7 @@ Other renderers
 Blackfriday is structured to allow alternative rendering engines. Here
 are a few of note:
 
-*   [github_flavored_markdown](https://godoc.org/github.com/shurcooL/github_flavored_markdown):
+*   [github_flavored_markdown](https://pkg.go.dev/github.com/shurcooL/github_flavored_markdown):
     provides a GitHub Flavored Markdown renderer with fenced code block
     highlighting, clickable heading anchor links.
 
@@ -279,21 +293,28 @@ are a few of note:
 *   [markdownfmt](https://github.com/shurcooL/markdownfmt): like gofmt,
     but for markdown.
 
-*   [LaTeX output](https://github.com/Ambrevar/Blackfriday-LaTeX):
+*   [LaTeX output](https://gitlab.com/ambrevar/blackfriday-latex):
     renders output as LaTeX.
 
+*   [bfchroma](https://github.com/Depado/bfchroma/): provides convenience
+    integration with the [Chroma](https://github.com/alecthomas/chroma) code
+    highlighting library. bfchroma is only compatible with v2 of Blackfriday and
+    provides a drop-in renderer ready to use with Blackfriday, as well as
+    options and means for further customization.
+
 *   [Blackfriday-Confluence](https://github.com/kentaro-m/blackfriday-confluence): provides a [Confluence Wiki Markup](https://confluence.atlassian.com/doc/confluence-wiki-markup-251003035.html) renderer.
 
 *   [Blackfriday-Slack](https://github.com/karriereat/blackfriday-slack): converts markdown to slack message style
 
-Todo
+
+TODO
 ----
 
 *   More unit testing
-*   Improve unicode support. It does not understand all unicode
+*   Improve Unicode support. It does not understand all Unicode
     rules (about what constitutes a letter, a punctuation symbol,
     etc.), so it may fail to detect word boundaries correctly in
-    some instances. It is safe on all utf-8 input.
+    some instances. It is safe on all UTF-8 input.
 
 
 License
@@ -305,6 +326,10 @@ License
    [1]: https://daringfireball.net/projects/markdown/ "Markdown"
    [2]: https://golang.org/ "Go Language"
    [3]: https://github.com/vmg/sundown "Sundown"
-   [4]: https://godoc.org/gopkg.in/russross/blackfriday.v2#Parse "Parse func"
+   [4]: https://pkg.go.dev/github.com/russross/blackfriday/v2#Parse "Parse func"
    [5]: https://github.com/microcosm-cc/bluemonday "Bluemonday"
-   [6]: https://labix.org/gopkg.in "gopkg.in"
+
+   [BuildV2SVG]: https://travis-ci.org/russross/blackfriday.svg?branch=v2
+   [BuildV2URL]: https://travis-ci.org/russross/blackfriday
+   [PkgGoDevV2SVG]: https://pkg.go.dev/badge/github.com/russross/blackfriday/v2
+   [PkgGoDevV2URL]: https://pkg.go.dev/github.com/russross/blackfriday/v2