[FEATURE] ✨ Add gfm-stylesheet

Add a GitHub Flavored Markdown Stylesheet,
with the keyword »gfm«.

Author: pixelbrackets

README.md

@@ -96,6 +96,7 @@ Mirror https://github.com/pixelbrackets/html5-mini-template
   one of following reserved [keywords](https://gitlab.com/pixelbrackets/html5-mini-template/-/blob/1.2.1/src/Html5MiniTemplate.php#L18)
   which then creates a link to a CDN of the selected CSS framework
   - [`bootstrap`](https://github.com/twbs/bootstrap/)
+  - [`gfm`](https://github.com/pixelbrackets/gfm-stylesheet/)
   - [`milligram`](https://github.com/milligram/milligram/)
   - [`minicss`](https://github.com/Chalarangelo/mini.css/)
   - [`mui`](https://github.com/muicss/mui/)

src/Html5MiniTemplate.php

@@ -19,6 +19,7 @@ class Html5MiniTemplate
     protected $listOfStylesheets = [
         'bootstrap' => 'https://cdn.jsdelivr.net/gh/twbs/[email protected]/dist/css/bootstrap.min.css',
         'example' => '/assets/css/stylesheet.css?v=1',
+        'gfm' => 'https://cdn.jsdelivr.net/gh/pixelbrackets/[email protected]/dist/gfm.min.css',
         'milligram' => 'https://cdn.jsdelivr.net/gh/milligram/[email protected]/dist/milligram.min.css',
         'minicss' => 'https://cdn.jsdelivr.net/gh/Chalarangelo/[email protected]/dist/mini-default.min.css',
         'mui' => 'https://cdn.jsdelivr.net/gh/muicss/[email protected]/packages/cdn/css/mui.min.css',