Improve GridMapping API docuemntation

[konstntokas]

• Enhanced GridMapping API documentation.

Closes #28

Checklist:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/
• Changes documented in CHANGES.md
• CI checks pass
• Test coverage remains or increases (target 100%)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.95%. Comparing base (c4c9deb) to head (e25a439).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #34   +/-   ##
=======================================
  Coverage   98.95%   98.95%           
=======================================
  Files          20       20           
  Lines        2018     2018           
=======================================
  Hits         1997     1997           
  Misses         21       21           

☔ 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.