Update nomaterial branch

[andi34]

Fixes https://github.com/mhausenblas/mkdocs-deploy-gh-pages/issues/227

• Cherry-Picked applying commits from master branch to get in sync
• updated Docker file:
  • use python:3.11-alpine3.18
  • removed unneeded run line
• updated example for nomaterial action
• install mkdocs by default, no need for an own requirements.txt now
• updated action example to use checkout@v4

[andi34]

Add also required mkdocs by default?

[andi34]

Used on https://github.com/PhotoboothProject/PhotoboothProject.github.io

https://photoboothproject.github.io/

[andi34]

Made draft because of personal changes since this PR was never reviewed and no feedback given.