add PR check that CHANGELOG was modified

Author: ezhang6811

.github/workflows/pr-build.yml

@@ -10,6 +10,37 @@ permissions:
   contents: read
 
 jobs:
+  changelog-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          
+      - name: Check CHANGELOG
+        run: |
+          # Check if PR is from pre-release or post-release workflow
+          if [[ "${{ github.event.pull_request.user.login }}" == "aws-application-signals-bot" ]]; then
+            echo "Skipping check: PR from aws-application-signals-bot"
+            exit 0
+          fi
+          
+          # Check for Skip Changelog label
+          if echo '${{ toJSON(github.event.pull_request.labels.*.name) }}' | jq -r '.[]' | grep -q "Skip Changelog"; then
+            echo "Skipping check: Skip Changelog label found"
+            exit 0
+          fi
+          
+          # Fetch base branch and check for CHANGELOG modifications
+          git fetch origin ${{ github.base_ref }}
+          if git diff --name-only origin/${{ github.base_ref }}..HEAD | grep -q "CHANGELOG.md"; then
+            echo "CHANGELOG.md entry found - check passed"
+            exit 0
+          fi
+          
+          echo "It looks like you didn't add an entry to CHANGELOG.md. If this change affects the SDK behavior, please update CHANGELOG.md and link this PR in your entry. If this PR does not need a CHANGELOG entry, you can add the 'Skip Changelog' label to this PR."
+          exit 1
+
   build:
     runs-on: ubuntu-latest
     strategy: