Initial draft for high quality processing button, fron Jens.

[paperdigits]

Made a PR for @jenshannoschwalm from https://github.com/darktable-org/dtorg/issues/252

[paperdigits]

I don't see any issues tagged in the darktable repo for this...

[elstoc]

This documentation is for https://github.com/darktable-org/darktable/pull/15910

[github-actions[bot]]

This pull request has not had any activity in the past 60 days and will be closed in 365 days if not updated. Please verify it has no conflicts with the master branch and rebase if needed. Please add a comment if you need help or give permission to other people to finish your work.

[elstoc]

Ok I'm gonna merge and copy-edit this, and then raise an issue to update the bottom-bar screenshot