Review/fix HTML/Markdown parsing

[marrus-sh]

Discussed in #17

^{Originally posted by single-right-quote September 13, 2021}
so we can use ’ instead of ’

Edit:

posting the above text (as rendered, not as from the markdown source for this conversation) as a markdown post renders

so we can use ’ instead of ’

while parsing #x2019 as a hashtag. this is silly. we should do as markdown does, namely, rendering that as

so we can use ’ instead of ’

I consider this a bug, so I’m gonna just File A Bug for it. It could be worth sending this upstream to GlitchSoc if it’s easy, but it might wind up significantly changing behaviour.