ci: Add gh-check-pr-is-updated to the CI workflow (#160)

Author: xmnlab

.github/workflows/main.yaml

@@ -8,6 +8,25 @@ on:
     branches: [ main ]
 
 jobs:
+  check-branch:
+    if: ${{ github.event_name == 'pull_request' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    concurrency:
+      group: check-pr-${{ github.ref }}
+      cancel-in-progress: true
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Check if the PR's branch is updated
+        uses: osl-incubator/[email protected]
+        with:
+          remote_branch: origin/main
+          pr_sha: ${{ github.event.pull_request.head.sha }}
+
   build:
     runs-on: ubuntu-latest
     concurrency: