Incorrect return types for `parseChunk` and `flush`.

[muzam1l]

The return types of functions parseChunk and flush are incorrectly typed as Iterator<T> in Typescript declarations while it is supposed to be Iterable<T>!

This makes Typescript error out for spread operator ... as well as for loops.

I can make the change if PR's are welcomed.

Thanks.

[eshaz]

Thanks for finding this. Pull requests are always welcomed and would be appreciated.

[unanmed]

Hi, I'm using this great library and I noticed this issue hasn't been addressed yet, and I'd like to help fix it.

In addition, I was thinking of adding some comments to the type definitions.

I'll proceed with the changes and submit a PR soon if there are no objections.

Thanks.

[eshaz]

Hello, go ahead and submit a PR. PRs are always welcome.