@babel/parser: expose a TypeScript definition file from package

[AviVahl]

This allows the new parser package to be used in TypeScript projects, with static type checking and auto-completions. IDEs like VSCode will use this to show auto completions even in JavaScript projects, which is a huge benefit to users wanting to use the parser directly.

This PR follows the auto-generated .d.ts that was added to @babel/types in #7101

• took outdated DefinitelyTyped babylon .d.ts and updated it using new site's documentation.
• added "typings" folder to package, with the new .d.ts
• connected new .d.ts via package.json's "types" field. also adjusted "files" so folder will be published.
• definition file uses TypeScript 2.9's new import('package').Type syntax.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/8392/

[AviVahl]

Hey babel team,
Could anybody check this out?
Would be great to get built-in type checking for the next 7 beta :)

[AviVahl]

@hzoo any chance this could be reviewed/merged in time for the 7.0.0 stable release?

[43081j]

It would be incredibly useful to get this merged and eventually achieve the same goal for all other packages, too.

At the minute you can't mix and match DT types as they will conflict. If using the traverse package for example, you will not be able to use the community types combined with @babel/types, you will have to go back to @types/babel-types.

[xtuc]

Sorry, it seems that I missed that before.

I agree that this would be very useful. Unfortunately, I think that we won't be able to maintain it, it would be great if you can report any mistakes/outdated def here.

[xtuc]

A Flow to TypeScript transpiler would be very usefull, since Babel has the support for both, it should be pretty easy :)

[AviVahl]

Thanks for merging!

[mgroenhoff]

Is anyone already removing the typings for babel__parser on DefinitelyTyped?
https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/babel__parser