feature idea: aiohttp patch

[joemarshall]

I think aiohttp (client only) would be quite easy to patch because it is already async (and pyodide has an event loop), so it could just defer nicely to fetch.

I have a dependency on it according to my lock files, but right now I think it isn't used, so I don't urgently need to patch, but I might get round to it at some point.