Convert templates from .hbs to .tsx

[cspotcode]

I was nerd-sniped by our discussion on Discord, so I tried to automatically convert the .hbs into .tsx This is as far as I got. convert.ts attempts to use a third-party library to do the conversion. It complains about some stuff that I've been manually find-and-replacing.

TODO

• [ ] converge item and props variables. Using both was a hack because the hbs to jsx converter uses item for #each iteration but props for the top-level props object.
• [ ] assign a type to the input of each component; right now it is implicit any
• [ ] switch to preact? it's what Gerrit0 was using in library-mode branch
• [ ] write a Theme interface; import and consolidate all functions into a single Theme instance
• [x] fix IfCond invocations to pass a boolean wrapped in {}
  • [ ] Ideally remove IfCond entirely, but would be annoying for an MVP
• [x] implement IfSignature
• [x] implement Markdown
• [ ] implement Collapse: what even is this?
• [ ] fix the inline className conditionals that I hacked away to please the converter