Let's put aiohttp-sse under the aio-libs org on PyPI

[webknjaz]

See the details @ https://github.com/orgs/aio-libs/discussions/26.

For this, we'll need somebody with Owner privileges to either give me access on PyPI (the username there is the same — webknjaz) or be invited to the org by me (for that I'd need the username of such an individual).

As a bonus, this will also allow us to set up secretless publishing from GHA to PyPI and get rid of the in-repo secrets.

cc @jettify