Feature request: add or remove watched directories while `async for changes in awatch('/path/to/dir')` is iterating

[tovrstra]

I was hoping to use watchfiles, but it seems impossible to add or remove watches while iterating over changes. (?)

Such a feature would be useful for more complex programs where one coroutine or thread is responsible for deciding which directories to (un)watch, typically not recursively, while another part of the program is in charge of processing file system events.