Support small fixes in production branch

[tillrohrmann]

At the moment we assume that production is a strict prefix of main. That's why when we create a new documentation release, we simply push main to production. This is problematic if one wants to fix some smaller things in the production branch (e.g. correcting a typo) because it often causes the prefix property to be violated (e.g. if main already contains documentation about a new feature) and thereby breaking the release workflow.

Right now, if production diverges from main, then one needs to manually push main to production. This has the advantage that one usually checks what are the differences between the branches and cherry-picks them over if something is missing.

A simple alternative could be to force push from main to production on release. This has the downside/danger that fixes that were only merged into production but not main might get lost.

A more involved solution could be to version our docs releases and introducing release branches for the different releases. The release branches would always be deployed and creating a new release from main would result in cutting a new release branch. Also here, the danger is that some fixes that happen on a release branch might get not be ported to the latest release branch. The upside is that these fixes wouldn't be lost due a force push.