Closes academicpages#2287, academicpages#534 with updates to documentation, better emoji generation

Author: rjzupkoii

Gemfile

@@ -1,10 +1,11 @@
-source "https://rubygems.org"
+source 'https://rubygems.org'
 
 group :jekyll_plugins do
-  gem "jekyll"
-  gem "jekyll-feed"
+  gem 'jekyll'
+  gem 'jekyll-feed'
   gem 'jekyll-sitemap'
-  gem "webrick", "~> 1.8"
+  gem 'jemoji'
+  gem 'webrick', '~> 1.8'
 end
 
-gem "github-pages"
+gem 'github-pages'

_config.yml

@@ -300,7 +300,9 @@ plugins:
   - jekyll-gist
   - jekyll-feed
   - jekyll-redirect-from
-# mimic GitHub Pages with --safe
+  - jemoji
+
+# Mimic GitHub Pages with --safe
 whitelist:
   - jekyll-paginate
   - jekyll-sitemap

_pages/markdown.md

@@ -30,6 +30,9 @@ redirect_from:
   * Orange circle: building
   * Red X: error
   * No icon: not built
+* Academic Pages uses [Jekyll Kramdown](https://jekyllrb.com/docs/configuration/markdown/), GitHub Flavored Markdown (GFM) parser, which is similar to the version of Markdown used on GitHub, but may have some minor differences. 
+  * Some of emoji supported on GitHub should be supposed via the [Jemoji](https://github.com/jekyll/jemoji) plugin :computer:.
+  * The best list of the supported emoji can be found in the [Emojis for Jekyll via Jemoji](https://www.fabriziomusacchio.com/blog/2021-08-16-emojis_for_Jekyll/#computer) blog post.
 
 ## Resources
  * [Liquid syntax guide](https://shopify.github.io/liquid/tags/control-flow/)