MD Composer Extras

Add some formatting option in your Discourse composer : underline, center, align right, justify and strikethrough

For more informations, see :

• English : https://meta.discourse.org/t/md-composer-extras/118912
• Français : https://www.mon-discourse.fr/themes/md-composer-extras/

Wrap support by thw26 : https://github.com/thw26

I took some parts of the Iconified Header Links and Slick Image Gallery theme components made by Johani :

https://meta.discourse.org/t/iconified-header-links/86307 (adding fa5 icons in the theme component) https://meta.discourse.org/t/slick-image-gallery/81952 (manager the translations inside the theme component)