uasyncio.queues: Add simple implementation of asynchronous queues for uasyncio

Hi, I've added simple port of asyncio.queues.Queue. It can be a bit slow, but works well for me.
For testing:
```bash
cd uasyncio.queues/tests
micropython test.py
```
That would complicate testing somewhat - would need to run them as test/test_*, etc.

Plus naming unit tests and not unit test as test_* would be confusing on its own. So, no obvious and definitive solution (the reason why it is currently the way it is), I guess I'll try to stick with example_*.py convention for new stuff, see if it sticks, and then maybe rename older files.