chore(ci): move block pr merge to its own workflow

.github/workflows/block_merge.yml

@@ -0,0 +1,18 @@
+name: Block PR merge
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  BlockMerge:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Check Commit to Squash
+        run: |
+          set -e
+          git log origin/${{ github.base_ref }}..origin/${{ github.head_ref }} --format=%s | ( ! grep -e "^f [0-9a-f]\+" -q )

.github/workflows/continuous-integration.yml

@@ -92,19 +92,6 @@ jobs:
           echo "Debug: ccache statistics (after the tests):"
           ccache -s
 
-  BlockMerge:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-20.04
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-
-      - name: Check Commit to Squash
-        run: |
-          set -e
-          git log origin/${{ github.base_ref }}..origin/${{ github.head_ref }} --format=%s | ( ! grep -e "^f [0-9a-f]\+" -q )
-
   ##################################
   # Releasing and Testing Packages #
   ##################################