Allow using other async libraries

[JuniorJPDJ]

The only thing holding us from doing this is one asyncio gather call and HTTP library.
We could switch to httpx:
https://www.python-httpx.org/async/#supported-async-environments

[obnoxiousmods]

Was going to actually open an issue to this repo saying you guys should consider using httpx instead of aiohttp

Is an awesome library, it uses AnyIO itself so it supports trio, curio, and asyncio + much easier to write + use than aiohttp