Deploy FairGBM read-the-docs documentation

[AndreFCruz]

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• LightGBM makes available their official documentation at https://lightgbm.readthedocs.io/en/v3.3.2/
• FairGBM features changes to the C API, new parameters, and other changes to the Python API
• We should build and deploy our own "read-the-docs"-style documentation specifically for FairGBM;