Connect to readthedocs.io

[janmandel]

Create documentation at https://wrfx.readthedocs.io and set up automated updates. https://wrfxpy.readthedocs.io is not updating.

[janmandel]

Regenerated docs by sphinx-quickstart 7292f52

Bulding html works fine fd29815

Test installation at https://demo.openwfm.org/web/wrfxpy/docs/build/html/ OK

But generating docs at https://wrfx.readthedocs.io/en/latest/ fails, tries to install gdal for some reason