refactor: improve Wdk export

[EdJoPaTo]

the Wbk interface has a lot of duplicate types which result in easy errors.
This removes a lot of these duplicates and the exact types of the functions are used.
Minor downside: types like type Url = string get simplified sometimes by TypeScript and look like string afterwards.

This should not breaking as long as no one used simplify or parse as an object (why should someone do that) (look at the tests/general to see what I mean).

very likely conflicts with #100 but this can easily be extended as #100 would only be the change in index.ts with this Pull Request.

[maxlath]

This should not breaking as long as no one used simplify or parse as an object

Ah yes, that's because, for some reason, when you do import * as parse from './helpers/parse_responses.js', then parse is an object with null as prototype; so when should does its nasty hack to extend the Object prototype, objects built with import/export * are not affected. There is a work-around though: should(parse).be.an.Object()

[EdJoPaTo]

I completely removed the src/types/wbk.ts as its now done in src/wikibase-sdk.ts. Your rebase didnt delete that file (probably because of a merge conflict).
Its obsolete now and should be removed as this PR is merged 😇

[EdJoPaTo]

There is a work-around though: should(parse).be.an.Object()

It should be this way anyway to be used with Typescripts strict null checks. I have a (messy) local branch for that already 😇

[maxlath]

I now removed src/types/wbk.ts in 41841fa