ci: register a dummy test_build_images workflow which will be completed in a separate PR (#947)

Author: NickLarsenNZ

.github/workflows/pr_test_build_images.yaml

@@ -0,0 +1,15 @@
+---
+name: Test Build Images
+
+on:
+  workflow_dispatch:
+  pull_request:
+    branches: [main, 'release/*']
+    # For now, we run on all paths, but if the products could be moved into a subdirectory, we could match on that
+    # paths: []
+
+jobs:
+  dummy:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo TODO