Create label to trigger Quay images job

Currently we're facing mainly 2 issues:

1. Images overflow in our [quay.io](quay.io/kuadrant/) repo
2. Pull requests coming from forks cannot trigger the build and push of the images

It would be good to have a label or a comment that administrators of Kuadrant org can assign to any PR in order to allow the trigger of the required quay job.

This needs to be applied to every Kuadrant repo.

Something that's been used by k8s that could be of help is https://prow.k8s.io/command-help#ok_to_test.

No files or tests are named. Start by comparing the CI configuration across the Kuadrant repositories and read the referenced Prow ok-to-test documentation. Define how an administrator-applied label or comment authorizes image builds for forked pull requests, then verify the behavior across every repository.

Written by the indexing model from the issue text.