Fix GitHub CI, test 3.11 for XS9 (and 3.12 and 3.13 for future updates) and fix pylint errors

[bernhardkaindl]

This PR has all changes in one, I started to split them into smaller PRs (#143 and #144 so far):

• Fix GitHub CI, test 3.11 for XS9 (and 3.12 and 3.13 for future updates) and fix pylint errors
• Fix Markdown linting using markdownlint-cli
• Use pre-commit to check formatting using darker and other quick checks.

[coveralls]

Pull Request Test Coverage Report for Build 11850148463

Details

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• 13 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.02%) to 83.691%

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Files with Coverage Reduction	New Missed Lines	%
xcp/xmlunwrap.py	2	92.31%
xcp/accessor.py	2	89.47%
xcp/cpiofile.py	3	75.26%
xcp/compat.py	6	78.57%

Totals
Change from base Build 9109272969:	0.02%
Covered Lines:	2807
Relevant Lines:	3354

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💛 - Coveralls

[bernhardkaindl]

Obsoleted the the CI PR series