fix: eliminate circular dependency index.ts-> parsing.ts-> index.ts

[DavidSanwald]

types in index.ts have been moved to types.ts, a function defined in index.ts has been moved to parsting.ts, next to its use

fixes #43

[DavidSanwald]

it could be the case, that the types in index.ts were intended to be part of the public module surface. I didn't check yet, therefore it's currently still a draft.

[DavidSanwald]

Ah, now I see the JSDoc strings. Of course everything what's currently public, should remain public for now, I'll adjust that the coming days.

But can could it be that the case, that the module API exposes a lot of things, that wouldn't need to be public?