add notebook with recipe for how to go from PWS CSV data to xarray inluding example data

[JochenSeidel]

• [x] closes #34
• [ ] Tests added and passed if fixing a bug or adding a new feature
• [x] All code checks from pre-commit passed
• [x] Added an entry in the CHANGELOG.md file

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (61c4063) to head (8c7d978). Report is 19 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #55 +/- ## ========================================== Coverage 100.00% 100.00% ========================================== Files 3 4 +1 Lines 43 321 +278 ========================================== + Hits 43 321 +278 ```

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[cchwala]

Thanks @JochenSeidel for this contribution. Ready to merge 🎉