add changelog reminder pipeline for PRs

.github/workflows/check-changelog.yml

@@ -0,0 +1,19 @@
+name: Verify CHANGELOG.md is updated
+
+on: [pull_request]
+
+jobs:
+  check:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - uses: mskelton/changelog-reminder-action@v3
+        with:
+          message: >
+            Oops! Looks like you forgot to update the changelog.
+            When updating CHANGELOG.md, please consider the following:
+              - Changelog is read by country implementors who might not always be familiar with all technical details of OpenCRVS. Keep language high-level, user friendly and avoid technical references to internals.
+              - Answer "What's new?", "Why was the change made?" and "Why should I care?" for each change.
+              - If it's a breaking change, include a migration guide answering "What do I need to do to upgrade?".