Add a timeout for running the test suite.

Author: freakboy3742

.github/workflows/ci.yml

@@ -131,6 +131,7 @@ jobs:
       uses: beeware/.github/.github/actions/install-briefcase@main
 
     - name: Test App
+      timeout-minutes: 15
       run: briefcase run ${{ matrix.briefcase-target }} --test ${{ matrix.briefcase-run-args }}
 
     - name: Package