Add docs dir branch

[bitsondatadev]

Adding 1.4.0/1.4.1 versioned MkDocs builds (they both use the same version) to an orphaned docs branch in the main repository.

This will enable the step to add the docs at build time, while avoiding having these docs show up in the search index of local repositories.

Note: I'm attempting to move from using a branch per release to a single branch. This will likely work better to avoid having to create new branches in main every release, make retroactive updates much faster.