Add changelog warning

.github/workflows/changelog.yml

@@ -0,0 +1,18 @@
+name: Check CHANGELOG.md
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  check-changelog:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@main
+      - name: Check if CHANGELOG.md has been modified
+        run: |
+          if git diff --name-only ${{ github.event.pull_request.base.sha }} ${{ github.sha }} | grep -q "CHANGELOG.md"; then
+            echo "CHANGELOG.md has been modified. Good job!"
+          else
+            echo "::warning::CHANGELOG.md has not been modified. Please update the changelog."
+          fi