Add GitHub Actions, linting and formatting

[jams2]

Adds:

• tox config
• GitHub action to run the tests
• ruff config for formatting and linting
• pre-commit config (that runs ruff)
• GitHub action to lint the code using the pre-commit config
• a .git-blame-ignore-revs file with hashes of the commits that apply fixes to the issues raised by ruff and pre-commit