Create automated wiki script in a `workflow_dispatch` action

[Marvin-Brouwer]

The purpose of this script is to submodule this repo's wiki and copy over the contents of the ./.github/wiki folder. That way we have full wiki pull requests.

• https://stackoverflow.com/questions/10642928/how-to-pull-request-a-wiki-page-on-github
• https://www.growingwiththeweb.com/2016/07/enabling-pull-requests-on-github-wikis.html
• https://docs.github.com/en/communities/documenting-your-project-with-wikis/adding-or-editing-wiki-pages#cloning-wikis-to-your-computer
• https://gist.github.com/subfuzion/0d3f19c4f780a7d75ba2
• https://git-scm.com/book/en/v2/Git-Tools-Submodules