Add note about project move to SourceHut

Replaced Github workflow with build.sr.ht config

Moved project to SourceHut

git ignore __pycache__ directories

Fixed user token variable

Update copyright years

Added Github actions build

Replaced setup.py with pyproject.toml

Added ssl_context to constructor, consider logger and user_token private

Set network timeout and close connection after use

Extracted listenbrainz_submit from othe projects into own module