[Doc] no documentation for async with

[youkaichao]

Surprisingly, I find the documentation https://docs.python.org/3/library/asyncio.html does not even mention async with . However, this kind of usage is quite popular in libraries such as aiohttp https://github.com/aio-libs/aiohttp .

[blhsing]

https://docs.python.org/3/library/asyncio.html is an overview page and should not contain details of indivdual constructs and functions.

async with is formally documented in https://docs.python.org/3.9/reference/compound_stmts.html#the-async-with-statement and mentioned in https://docs.python.org/3/library/asyncio-task.html and https://docs.python.org/3/library/asyncio-sync.html , which are referenced in the overview page.