Simplify docs build and deploy workflow

[LiamConnors]

Currently the Python graphing library docs use the following repos as part of the docs build and deploy process:

• graphing-library-docs
• plotly.py
• plotly.py-docs (two different branches)
• documentation

Additionally, the docs for the other languages (R, Julia, Matlab, .net) mean there are about eight repos involved in the build and deploy process.

This issue is to track simplifying this process