Closes #44 Closes #118 Relates #100

This basically duplicates #100 at this point. See #100 for up and downsides of this approach.

I was initially intending to get rid of a lot more dependencies (like the dependencies for handling html) and use svelte-ast-print instead, but this was opening too many issues at the same time. That's why I opted to "only" switch to acorn and esrap here, the rest can be done later.

Relevant PR's / issues

• Rich-Harris/esrap#18
• Rich-Harris/esrap#19
• sveltejs/esrap#44
• sveltejs/esrap#47
• sveltejs/esrap#51
• sveltejs/esrap#45
• sveltejs/esrap#52

Benefits

• closer to other tools in the svelte ecosystem
• Faster bundling (~33% speed improvement locally from 4s to 3s, probably more with #371)
• Smaller bundle (locally 2.6MB vs 3.6MB)
• more consistent formatting than the strange things we sometimes experienced with recast
• we are in full control of the printing, as we can control esrap

Downsides

• Our custom typing for TSEstree as no good public alternative exists, that matches acorns output. We do have @typescript-eslint/types but that was just the one with the smallest pain points. Still exploring other options.