Dealing with too long README.md

[viktorvan]

Is your feature request related to a problem? Please describe.

The README.md is getting very long, and not that easy to navigate. I find it hard to find (and add) information there. And I think we might have the same issue with the README for ActiveLogin.Authentication.

I just feel that if I add more code examples in the README right now it will lead to information overload and the important stuff in the README about why you should use the library, our design decisions and sponsors will just get hidden away.

The README just won't scale when we have to add information, examples and samples for all the types of numbers we plan to support in the future.

I have looked at some other open source libraries, for example FsCheck and I think it is using a great approach that I have seen in many other open source libraries:

1. At the top of their github page they have a link to a separate documentation site using github-pages.
2. On the documentation site they have an api-reference, which I assume is auto-generated, with documentation on the functions and parameters in the api with relevant links to code on github.

Should we maybe look into something like this for ActiveLogin.Identity/Authentication? Or at the very least we should add a table-of-contents on the top of our README to make it easier to navigate and find information.

[PeterOrneholm]

Not solving all of these issue, but my PR #115 is moving in this direction with TOC etc.