Add optional typescript type definitions

[tillsc]

This allows typescript users to:

• Use typing in TSX :)
• import ... from "complate-stream" (since typescript doesn't support npm main property)

I didn't add tests for typescript since I didn't want to add typescript as developmentDependency. But maybe we should do something like that (later?).

[tillsc]

I'll check some more stuff... cu later... sorry

[tillsc]

Sorry thought I missed something ... but I didn't :)

[FND]

squashed as 944f45c3b265f7101b19256ca6740c88966008ba and released as v0.16.2 - sorry for unnecessarily delaying this with irrational perfectionism; the only way to make this work is to enable people to actually use it

[tillsc]

Thx!