Allow to upload translations to crowdin via when:manual

Background

In #122 (closed) we are tackling translation workflow integration with XTM. One problem we encountered is that XTM doesn't have direct Crowdin support so it's impossible for our TMs to takeover/execute the crowdin parts of our translation workflow autonomously.

Checking out the relevant version of the codebase, installing all the dependencies to execute the crowdin sync script to upload the translations presents a significant hurdle for our TMs. One potential option to help with that would be to upload the translation via GitLab CI and making it executable for the TMs via when:manual

What to do

Add a Job to upload translations to crowdin manually via when: manual. For convenient debugging/testing it should be possible to override the crowdin project to upload to a temporary/test project on crowdin.