Mix anyio and asyncio code.

[laker-93]

Things to check first

• I have searched the existing issues and didn't find my feature already requested there

Feature description

I am looking for documentation to advise if mixing anyio and asyncio code is supported. My use case is a large Python 3.8 asyncio code base. I'd like to use anyio in order to incrementally use SC for creating and cancelling tasks. I have run numerous tests using a mix of both and the behaviour looks correct. However I am aware of #374 which occurs when mixing between anyio 3.x and asyncio where the CancelledError does not propagate out of the task group context manager. Are there any other gotchas one should be aware of when using a mix of asyncio and anyio for task management?

Use case

Incrementally converting from normal asyncio task management to Structured Concurrency with anyio.