Use Dokka and Mkdocs to generate documentation

[stevenzeck]

NOTE: This PR is for the branch main. This PR adds a new GitHub action to generate documentation. It does this by the following:

1. Every time a push is made to the branch main, it runs the action. After installing the dependencies and everything, it runs Dokka to generate markdown files for each of the submodules.
2. After that is complete, Mkdocs/mike is run to transform the markdown to an HTML ready website that is committed to the gh-pages branch

Things to keep in mind for the future:

1. Whenever a push is made to main for a new release, make sure update-docs.yml is updated so that the LATEST_VERSION variable is the release number. Not sure if that version number can be pulled from an gradle file or not
2. Any pushes to main without a change in the release number will simply overwrite the previous documentation for that release number. This is useful for adding new documentation, changing verbiage in it, etc.

[mickael-menu]

1. Whenever a push is made to main for a new release, make sure update-docs.yml is updated so that the LATEST_VERSION variable is the release number. Not sure if that version number can be pulled from an gradle file or not

You can use the following to get the latest tag in the current branch matching the pattern [0-9]* (works with dots too somehow):

$ git describe --tag --match [0-9]* --abbrev=0
2.1.0

[mickael-menu]

Thanks, this will be very useful!