hint useful variables when manually triggering pipelines

every now and again I find myself triggering pipelines manually, e.g. because i want to investigate reproducibility issues.

my workflow is as follows:

1. notice that the package fails the "reproducible" job
   • but which one? luckily salsa-ci provides a way to narrow that down...
2. open the projects CI/CD-><kbd<Pipelines page in my browser
   • hit the Run pipeline
3. in a separate tab, navigate to the salsa-ci/pipeline documentation
   • notice that i need to set SALSA_CI_ENABLE_ATOMIC_REPROTEST=1
4. go back to the "Run pipeline" tab and in the Variables section fill in the variable-name and value i just looked up
5. finally "Run pipeline

i would like to get rid of the "look up documentation" step.

ideally, the Run pipeline page should present me with variables I can tweak (and some explanation what they do).

GitLab-CI can do this 😉