Add script to download example data files for SOLER workshop #3

[jgieseler]

This pull request adds a new section to the JupyterHub_Help.ipynb notebook to support Workshop 3. The main change is the inclusion of a script that downloads example data files needed for the workshop, ensuring participants can access the required data even if there are server connection issues.

Workshop 3 support:

• Added a new markdown cell introducing Workshop 3 and explaining the purpose of the data download script.
• Included a Python code cell that downloads and unpacks example data files from a GitHub repository into the user's data folder, handling the extraction and folder structure automatically.

[jgieseler]

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