Documentation site for different Norfair versions

[javiber]

• Added mike to mkdocs build.
• Deployed version 2.0 manually (in the future a new github action is needed)
• Changed the github pages config to deploy from the branch gh-pages
• Changed the existing github action, no need to deploy directly to pages now. But we re-porposed it to update a version called "dev" of the doc every time we push something to master. This new version gets pushed to gh-pages branch which is deployed to github pages automatically. (needs testing)