Update docs and CHANGELOG

Author: colinodell

CHANGELOG.md

@@ -6,6 +6,9 @@ Updates should follow the [Keep a CHANGELOG](https://keepachangelog.com/) princi
 
 ## [Unreleased][unreleased]
 
+### Added
+- Added a new `HighlightExtension` for marking important text using `==` syntax (#1100)
+
 ## [2.7.0]
 
 This is a **security release** to address a potential cross-site scripting (XSS) vulnerability when using the `AttributesExtension` with untrusted user input.

docs/2.x/extensions/highlight.md

@@ -0,0 +1,58 @@
+---
+layout: default
+title: Highlight Extension
+description: The HighlightExtension allows marking important text.
+redirect_from:
+  - /extensions/highlight/
+---
+
+# Highlight Extension
+
+This extension adds support for highlighting important text using the `==` syntax. For example, the Markdown:
+
+```markdown
+I need to highlight these ==very important words==.
+```
+
+Would be rendered to HTML as:
+
+```html
+<p>I need to highlight these <mark>very important words</mark>.</p>
+```
+
+Which could then be styled using CSS to produce a highlighter effect.
+
+## Installation
+
+This extension is bundled with `league/commonmark`. This library can be installed via Composer:
+
+```bash
+composer require league/commonmark
+```
+
+See the [installation](/2.x/installation/) section for more details.
+
+## Usage
+
+This extension can be added to any new `Environment`:
+
+```php
+use League\CommonMark\Environment\Environment;
+use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
+use League\CommonMark\Extension\Highlight\HighlightExtension;
+use League\CommonMark\MarkdownConverter;
+
+// Define your configuration, if needed
+$config = [];
+
+// Configure the Environment with all the CommonMark parsers/renderers
+$environment = new Environment($config);
+$environment->addExtension(new CommonMarkCoreExtension());
+
+// Add this extension
+$environment->addExtension(new HighlightExtension());
+
+// Instantiate the converter engine and start converting some Markdown!
+$converter = new MarkdownConverter($environment);
+echo $converter->convert('I need to highlight these ==very important words==.');
+```

docs/2.x/extensions/overview.md

@@ -40,6 +40,7 @@ to enhance your experience out-of-the-box depending on your specific use-cases.
 | [Front Matter] | Parses YAML front matter from your Markdown input |  `2.0.0` | |
 | **[GitHub Flavored Markdown]** | Enables full support for GFM. Automatically includes the extensions noted in the `GFM` column (though you can certainly add them individually if you wish): | `1.3.0` | |
 | [Heading Permalinks] | Makes heading elements linkable | `1.4.0` | |
+| [Highlight] | Mark text as being highlighted for reference or notation purposes | `2.8.0` | |
 | [Inlines Only] | Only includes standard CommonMark inline elements - perfect for handling comments and other short bits of text where you only want bold, italic, links, etc. | `1.3.0` | |
 | [Mentions] | Easy parsing of `@mention` and `#123`-style references | `1.5.0` | |
 | [Strikethrough] | Allows using tilde characters (`~~`) for ~strikethrough~ formatting | `1.3.0`  | <i class="fab fa-github"></i> |
@@ -121,6 +122,7 @@ See the [Custom Extensions](/2.x/customization/extensions/) page for details on
 [Front Matter]: /2.x/extensions/front-matter/
 [GitHub Flavored Markdown]: /2.x/extensions/github-flavored-markdown/
 [Heading Permalinks]: /2.x/extensions/heading-permalinks/
+[Highlight]: /2.x/extensions/highlight/
 [Inlines Only]: /2.x/extensions/inlines-only/
 [Mentions]: /2.x/extensions/mentions/
 [Strikethrough]: /2.x/extensions/strikethrough/

docs/_data/menu.yml

@@ -25,6 +25,7 @@ version:
             'Footnotes': '/2.x/extensions/footnotes/'
             'Front Matter': '/2.x/extensions/front-matter/'
             'Heading Permalinks': '/2.x/extensions/heading-permalinks/'
+            'Highlight': '/2.x/extensions/highlight/'
             'Inlines Only': '/2.x/extensions/inlines-only/'
             'Mentions': '/2.x/extensions/mentions/'
             'Smart Punctuation': '/2.x/extensions/smart-punctuation/'