Major refactoring: Callback & iterable support

[andywer]

Allows you to expose callbacks function. Works main-to-worker as well as worker-to-main.

It's a major refactoring, using the callbacks to implement the existing spawn() and expose() APIs. Also introduces support to return iterables and async iterables.

Closes #145. Closes #251.

• Implement callback support
• Implement iterable & async iterable support
• Add unit tests
• Test passing observable to worker
• Update documentation
• Check if bundled size can be decreased

[kylezimmerman]

Thanks for the awesome library @andywer, I'm really enjoying using it so far. This PR looks really cool, I'd love to be able to use async iterables.

Is this something your still working on?

[EmmanuelAAM]

Hi, I was taking a look at one of the issues of the repo and trying to find info about the possibility of using callbacks and I was wondering Is this PR gonna happen? Thanks for the amazing work with threads.js <3

[andywer]

@EmmanuelAAM Thanks for the kind words! I'm afraid this is on hold as there seemed to be limited interest and I currently don't have extra time to spend on it.