SIANXKE-407: Add pre-commit configuration and pipeline checks

[bernhard-hagmann]

Builds on #12

• Adds pre-commit configuration and pipeline checks
• Re-formats everything

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 63.80%. Comparing base (358ccfb) to head (c038653).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
django_cleanhtmlfield/fields.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #13   +/-   ##
=======================================
  Coverage   63.80%   63.80%           
=======================================
  Files           2        2           
  Lines         105      105           
=======================================
  Hits           67       67           
  Misses         38       38           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.