Add detailed message to changelog workflow (opensearch-project#19172)

Signed-off-by: Umarov Ismoiljon <hs.umarov21@gmail.com>
Co-authored-by: Andrew Ross <andrross@amazon.com>

Author: 2 people

.github/workflows/changelog_verifier.yml

@@ -16,3 +16,8 @@ jobs:
       - uses: dangoslen/changelog-enforcer@v3
         with:
           skipLabels: "autocut, skip-changelog"
+          changeIsMissingMessage: |
+            ❌ ERROR: No update to CHANGELOG.md found!
+            This project requires a changelog entry for every user-facing change.
+            Please add an entry to the changelog or ask a maintainer to add the skip-changelog label.
+            See https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#changelog for more details.