[Docs] Automate docs generation and exclude HTML from main branch

[DanielYang59]

Post from #4053 (comment):

• Add docs builder as an automatic workflow, I think we already have one jekyll-gh-pages.yml but it doesn't seem to be used
• Exclude generated HTMLs from main branch, we would need a dedicated branch just to host docs

This would also resolve:

• [Doc/Dev] Off-by-one errors for line numbers in documentation source #4038