Update README file.

README.md

@@ -1,13 +1,25 @@
 [![CI Status](https://github.com/vufind-org/vufind-marc/actions/workflows/ci.yaml/badge.svg?branch=dev)](https://github.com/vufind-org/vufind-marc/actions/workflows/ci.yaml)
+
 VuFind-Marc
 ===========
 
 Introduction
 ------------
 VuFind-Marc contains classes to handle [MARC records](https://www.loc.gov/marc/) in
-different carrier formats (ISO2709, MARCXML, MARC-in-JSON). This is part of the
-VuFind® project (http://vufind.org) but may also be useful for other purposes.
+different carrier formats. This is part of the [VuFind® project](http://vufind.org)
+but may also be useful for other purposes.
+
+Features
+--------
+VuFind-Marc provides functionality for reading MARC records and validating (linting)
+MARC 21 records. It supports standalone records as well as record collection files.
+Following carrier formats are supported:
+
+- [ISO 2709](https://en.wikipedia.org/wiki/ISO_2709)
+- [MARCXML](https://www.loc.gov/standards/marcxml/),
+- [MARC-in-JSON](https://web.archive.org/web/20151112001548/http://dilettantes.code4lib.org/blog/2010/09/a-proposal-to-serialize-marc-in-json/)
 
+Additional formats can be added as necessary.
 
 Installation
 ------------