TypeScript then babel

[fasterthanlime]

The original idea is 100% pure @paulcbetts tweetery, but I'm doing it for other selfish purposes.

Paul wanted to target a recent runtime (es2017?) with typescript and have babel fill in the gaps (with as few transformations as possible).

I'm just personally really pissed off at native async/await stacktraces being completely broken, so I wanted to go back to our previous strategy of turning async/await into Bluebird coroutines using babel.

Anyway, this pull request:

• Accepts a new configuration key, babel, for the typescript compiler
• Passes that config value (must be an object) wholesale, to the babel compiler (effectively what you'd put in your .babelrc, which electron-compilers ignores willingly afaict)
• Makes babel compile typescript's output, and combines both sourcemaps with sorcery
• Include the final sourcemap in the generated file, as an inline sourcemap

Note that this expects both typescript & babel to have (external) sourcemaps enabled.

I'm not sure it's mergeable as-is, but it's a start?!

[anaisbetts]

bless u @fasterthanlime, bless u