Merge pull request #1084 from DanielEScherzer/patch-1

README: add link to Pygments Highlighter extension

Author: colinodell

README.md

@@ -104,6 +104,7 @@ Custom parsers/renderers can be bundled into extensions which extend CommonMark.
  - [YouTube iframe extension](https://github.com/zoonru/commonmark-ext-youtube-iframe) - Replaces youtube link with iframe.
  - [Lazy Image extension](https://github.com/simonvomeyser/commonmark-ext-lazy-image) - Adds various options for lazy loading of images.
  - [Marker Extension](https://github.com/noah1400/commonmark-marker-extension) - Adds support of highlighted text (`<mark>` HTML tag)
+ - [Pygments Highlighter extension](https://github.com/DanielEScherzer/commonmark-ext-pygments-highlighter) - Adds support for highlighting code with the Pygments library
 
 Others can be found on [Packagist under the `commonmark-extension` package type](https://packagist.org/packages/league/commonmark?type=commonmark-extension).