data_preprocessing ERA5 and CDS examples

[vgro]

Description

I added a section on how to download climate data from the CDS and some simple preprocessing.
At the moment, only the ERA5 file shows the correct sidebar, I don't know where I need to include this to set out the structure properly.

Also, the jupiter notebook is not running and I don't know why exactly(apparently, it cannot find xarray, I think it might be earlier on).

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist

• Make sure you've run the pre-commit checks: $ pre-commit run -a
• [-] All tests pass: $ poetry run pytest

Further checks

• Code is commented, particularly in hard-to-understand areas
• [-] Tests added that prove fix is effective or that feature works

[codecov-commenter]

Codecov Report

Merging #139 (3ccd167) into develop (9b2fb9b) will not change coverage.
The diff coverage is n/a.

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  Coverage    94.06%   94.06%           
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  Files           11       11           
  Lines          472      472           
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  Hits           444      444           
  Misses          28       28           

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[davidorme]

LGTM - some minor things to fix up.

[davidorme]

LGTM.

[vgro]

First set of recipes to download and preprocess climate data. The location for this code and dummy data set will likely change in the future, there might be a separate package for pre-processing that includes topographic adjustment and scaling from low to high resolution (100 m).