Add documentation

[jenniferjiangkells]

CHANGES:

• Added mkdocs documentation site
• Tidied up README.md
• Tidied up pyproject.md
• Added contributing guidelines
• Added workflows for building, deploying documentation
• Added workflow for publishing
• Added PR template
• Added docstring to all functions

I did make some changes to Annotator that should technically be in another branch:

• Moved some methods around and reduced the number of abstract classes needed
• Moved lookup back as packaged data - this is because without the lookup tables configured, users would not be able to run MiADE at all and it's a bit of a pain to download the lookup data separately from a different source (given we already need to download med7 and spacy this might not add to the user experience).
• However the option to configure lookup table source from a different source is still in the configs - so now it is more flexible.

[jenniferjiangkells]

@jamesbrandreth FYI feel free to make changes / add things if I missed anything.

I've setup github actions that build and deploy the documentation page every time branch is merged to master (if i can get it working). We could make a MiADE slack or discord or something (I looked into discourse ala MedCAT and it's not as straightforward as I thought lol)

docs page is live here!

[jenniferjiangkells]

Might want to consider restricting Python to >3.8, <3.12 because MiADE cannot install run on 3.12