Require optional CI checks to succeed

[max-nextcloud]

Github can only require CI checks to always succeed. If they do not run because a path filter is in effect the merge will be blocked.

https://github.com/dorny/paths-filter#conditional-execution could enable conditionally running actions and still require them.

[vinicius73]

For reference: https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/troubleshooting-required-status-checks

[juliusknorr]

Started playing with this in https://github.com/nextcloud/richdocuments/pull/2518 one thing we might need is another job at the end that builds a summary and still passes if jobs are skipped.

[mejo-]

Given that we still have flaky Cypress tests from time to time, I'm not sure whether we want to make them mandatory in the first place :thinking: