Make package ready for PyPi publishing

[septatrix]

This PR contains multiple changes:

• Updated .gitignore to cover e.g. dist directory and egg files
• Updated README.md to contain the new setup instructions
• The required files for publishing (pyproject.toml, setup.cfg)
• The requirements.txt file was removed in favour of setup.cfg
• The script was moved into the syncmymoodle package as the main entrypoint
• Respect xdg-specification for config files (now tried in the order ${XDG_CONFIG_HOME:-~/.config}/syncmymoodle/config.json > $PWD/config.json > --config). I thought about dropping the implicit PWD one, what do you think?

TODO:

• [x] Swap author information in setup.cfg? I just added myself as I did not want to upload on your behalf @Romern. Are you fine with that? Otherwise we can also swap that and e.g. add myself as a maintainer.
• [x] Document xdg-specification compliance for the config in the docs. Currently it still instructs to use the current working directory.
• [ ] Potentially set up a Github Action for publishing in the long run
• [x] Add @Romern as a owner/maintainer on PyPi if he wants to

[septatrix]

What about the points in the checklist concerning you (i.e. PyPi metadata and permissions)?

[Romern]

Swap author information in setup.cfg? I just added myself as I did not want to upload on your behalf @Romern. Are you fine with that? Otherwise we can also swap that and e.g. add myself as a maintainer.

It's fine for me this way.

Add @Romern as a owner/maintainer on PyPi if he wants to

Maintainer would suffice.

[septatrix]

GH Actions can still be setup later (and would require more privileges from my side or require you to add a deploy key from PyPi to the GH secrets). Regarding the PyPi you can message me once you got you account setup. Therefore the remaining TODOs should be resolved.