Make the RTD documentation available

[MaelREBOUX]

• check the github project
• create RTD project
• check if the "latest" version is correctly build
• configure webhook integration
• add location to the nginx front container configuration
• add a section to the documentation pages

[MaelREBOUX]

Direct documentation is ok : https://georchestra-datafeeder.readthedocs.io/en/latest/

webhook configured

[MaelREBOUX]

nginx redirection configured : https://docs.georchestra.org/datafeeder/

[MaelREBOUX]

Hmmm : actually there is already an entry for the datafeeder that point to the main geOrchestra documenation.
https://docs.georchestra.org/georchestra/install_guide/apps/datafeeder/

@f-necas need to to homework (delete this chapter)