Ew4 tutorial further fixes

[stevehadd]

Fixed link to zarr loading tutorial in gallery, and added a Open in Colab button to that tutorial.

Docstrings

• Docstrings complete and follow Napoleon (google) style

Test Coverage

• All new code is covered by unit tests

Documentation

• [ X] Documentation is updated as required

Final Checks:

• [ X] If no generative AI was used, then tick this box

Alternatively, if generative AI was used, then confirm you have:

• Attributed any generative AI (such as GitHub Copilot) that was used in this PR. See our contributing guide for more information.
• Included the name and version of the tool or system in the pull request
• Described the scope of that use

Finally,

• [X ] Mark the PR as ready to review. Note - we encourage you to ask for feedback at the outset or at any time during the work.

[stevehadd]

@tennlee FYI - I figured out how to install from source on colab, as demonstrated in the branch:
https://github.com/stevehadd/PyEarthTools/blob/ew4_tutorial_further_fixes/docs/notebooks/data/Remote_Zarr_Loading.ipynb

So no rush now to do a release before the tutorial as colab use can proceed.

[stevehadd]

for information and completeness, it seems like you can't install an editable version of the library on colab (i.e. you need to use pip install /path/to/lib, without the -e option), so we may need a separate install fille for colab (other than requirements.txt) which doesn't have the -e flag. Will create in subsequent pull request.