Add option to download OpenMRG example data for 8 days

[cchwala]

• closes Add functionality to download small and large example datasets #56
• Tests added and passed if fixing a bug or adding a new feature (note that I do not test with the 8d data, just with the 5min_2h data from the last PR on this)
• All code checks from pre-commit passed
• Added an entry in the CHANGELOG.md file

This is an extension of #76

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.58%. Comparing base (61c4063) to head (9217e15).
Report is 47 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##              main      #89      +/-   ##
===========================================
- Coverage   100.00%   98.58%   -1.42%     
===========================================
  Files            3        7       +4     
  Lines           43      635     +592     
===========================================
+ Hits            43      626     +583     
- Misses           0        9       +9     

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