run test only on foreign PR

Author: Gummibeer

.github/workflows/run-tests.yml

@@ -8,6 +8,7 @@ on:
 
 jobs:
     test:
+        if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.repository
         runs-on: ${{ matrix.os }}
         strategy:
             fail-fast: false