docs: Update Module Author's and Maintainer's Docs.

Browse the updated docs here: https://git.h2t.iar.kit.edu/sw/armarx/meta/axii/-/blob/docs/update-docs/README.md

Bold = non-docs changes!

• Update top-level README cross-refs, old links.
• Move several topics from top-level README to dedicated documentations.
• Update maintainer's docs + axii self maintain print-release-message message
• Update module author's docs by documenting special variables
  • Rename variables to proper naming scheme used within Axii
  • Update variables within all modules using them
• Add white background to an image in order to be readable with dark themes
• Update output of axii w create to indicate activating workspaces and to reflect documentation