Add a manual SingleFileExporter

[theduke]

Allows manually exporting a set of types to a single file.

[Mattchine]

I like this. Thank you. Ps. I think this PR break when enable format feature.

[theduke]

Any feedback on this?

ps: @Mattchine it seems to work fine with format?

[aaronleopold]

Happy to help wherever needed get this merged, assuming it is within the scope of the project? Single file exporting (e.g. index.ts) is something I personally would really like to see, but understand if it isn't something the maintainer wants 🙂

[joaoantoniocardoso]

I'm also missing this feature - I hacked my way out to do the same thing in a custom build.rs, but it would be way better to have this feature merged/available.

[escritorio-gustavo]

Updated tests to expect type instead of `interface´

[escritorio-gustavo]

@NyxCode I'm not familiar with this part of the codebase, I think you should have a look

[gustavo-shigueo]

Apart from me cleaning up merge conflicts, this has been stale for over a year now, so I'll be closing this issue