Allow usage of some formatting in comments or replies

[supertassu]

ref WT:UTRS#Templates.

Technically speaking it would be easy to allow HTML formatting in comments/templates but I'd like to not do that. Either we could allow sanitized HTML via a library like html-sanitizer or allow using some markup language like https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet or even Wikitext.

[dqwiki]

Last UTRS used more a cheat sheet style. I would prefer to keep our sanitization local instead of outsourcing it, so I'd like to go the cheat sheet method, and wikitext is a great idea so we wouldn't have to train anyone in anything new.