Move to fork-based development

[ckolbPTB]

Currently we are all working on branches of the main gihub repo at PTB-MR. We want to transition to a workflow where everyone implements code on their own fork and then opens a PR to PTB-MR/mrpro. This will work for everything except changes to the docker files. These files can only be modified via PTB-MR/mrpro by a few people.

Steps to take:

• Ensure github actions using docker images work: review and merge Fetch docker names without github token #555
• Modify contributor guide to highlight fork-based development
• Restrict write access
• Fix comments of coverage and docs build for the public repos Fix public pull requests coverage and docs workflows comments  #585
• Add pre-commit hook to create notebooks also locally: adapt Update .ipynb notebooks from .py in pre-commit hook locally #537
  • create/update notebook from script but do not change script from notebook
  • add notebooks to git ignore and verify that does not create merge conflicts if notebooks are created locally, commit is pushed to origin and then git pull is called
• Subfolders for notebooks and example scripts: probably done in Update .ipynb notebooks from .py in pre-commit hook locally #537 which closes Split examples into scripts & notebooks subfolders #546
• Add colab support to notebook; done in Update .ipynb notebooks from .py in pre-commit hook locally #537
• Remove binder support and then close Remove the binder infrastructure #538, close Binder build takes > 15min #457

Please try to do this in smaller PRs not in one go such that it is easier to review.