Build system: switch out of Flow comment syntax

[tmcw]

Flow comment syntax is a continuing bother with prettier's formatting ( #709 ) and it sounds like its problems are very deep rooted, according to Christopher. Plus our continuing lack of Flow comments support because of a lack of upstream implementation mean that it just isn't... well, a good train to get on.

This'd mean switching to real Flow annotations, which would then mean switching to using a tool to strip them out, and then potentially going all the way and producing a single bundle to save on startup time

What do folks think here: are Flow comments something we should dig into or something that would be wise to cut from scope?

[arv]

I don't have an answer here but the way that documentation.js can work without a compile step is a good feature.

If we ever commit to a compile step then normal Flow annotations are just incredible.