Add publish docs workflow

Description

What's cooking? If this PR references an issue, please attach to the existing issue.

Makes docs branch available so github pages can be published.

[ ] New feature (non-breaking change which adds functionality)
[ ] Bug fix (non-breaking change which fixes an issue)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update

[ ] My PR is in the format of Add <project-name> recipe
[ ] My recipe is reproducible and explains everything needed to run successfully. If my code has external dependencies, I make mention of them.
[ ] My code is easily understandable and/or well-commented.
[ ] If my recipe requires a new category (e.g. creating a monitoring/ folder in devops/), I have encapsulated my project within its own subfolder so that others can add their own recipes as well.
[ ] If my recipe uses Prefect < 2.0, my code is within the prefect-v1-legacy/ folder.