dummy workflow to make pull_request_review work for forks

Author: myakove

.github/workflows/block-merge-if-not-approved.yml

@@ -1,5 +1,11 @@
 name: Block merge if not approved
-on: [pull_request_review, pull_request_target]
+on:
+  pull_request_target:
+  workflow_run:
+    workflows:
+      - Dummy pull_request_review workflow
+    types:
+      - requested
 
 jobs:
   block_pr_if_not_approved:

.github/workflows/dummy.yml

@@ -0,0 +1,11 @@
+name: Dummy pull_request_review workflow
+
+on: pull_request_review
+
+jobs:
+  dummy-workflow:
+    runs-on: ubuntu-latest
+    name: dummy workflow
+    steps:
+      - name: Explanation
+        run: echo "this is a dummy workflow that triggers a workflow_run; it's necessary because otherwise the repo secrets will not be in scope for externally forked pull requests"