Added documentation workflow

[classPythonAddike]

Added a documentation workflow, which uses sphinx to build the docs.

What it does -

• Installs git, python and clones the repo to a container
• Installs packages from the requirements.txt
• Builds the docs, removes unnecessary files, like source code, requirements.txt, setup.py, etc
• Configures git
• Then pushes the docs to the gh-pages branch, using a personal access token for auth

Setup:

1. Delete the gh-pages branch, and create a new gh-pages orphan branch
2. Create a personal access token in settings
3. Create a new secret by the name of ACCESS_TOKEN in this repository, and set its value to the token
4. Configure Github Pages to serve files from the root folder of the gh-pages branch
5. Change the github repository in line 5 of the sphinx-build.yml workflow

Once you commit your changes, the workflow should run again, and commit the docs to gh-pages. LMK if anything breaks! 😄