Set up run of e2e tests before merge

[benedeki]

Background

While there's a small app, kind of e2e test, it's not executed automatically as part of CI/CD.

Feature

Create an GitHub workflow that will run against PRs

NB!
It will contain cross repo/cross organization call.

Requirements

• Run the e2e test/app from within the branch to be merged.
• Suggested conditions to run
  • Approved by at least one reviewer (hint)
  • Successful build and unit and integration tests passing
  • (To consider) Label to skip the run, and consider the check success

Or consider using merge queue.