[WIP] Add notebooks to docs

[cchwala]

According to the documentation of readthedosc here it should be super easy to add the rendered notebooks in our docs. This PR does just that.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (975242b) 75.17% compared to head (879c8f8) 74.83%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #142      +/-   ##
==========================================
- Coverage   75.17%   74.83%   -0.35%     
==========================================
  Files          29       29              
  Lines        1112     1089      -23     
==========================================
- Hits          836      815      -21     
+ Misses        276      274       -2     

Flag	Coverage Δ
unittests	74.83% <100.00%> (-0.35%)	⬇️

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Files	Coverage Δ
pycomlink/processing/nearby_rain_retrival.py	100.00% <100.00%> (+4.00%)	⬆️
pycomlink/processing/wet_dry/nearby_wetdry.py	100.00% <100.00%> (ø)

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[cchwala]

...I have not yet managed to get this working...