feat(workflows): add fragments check workflow (feature/changelog)

Author: rayakame

.github/workflows/fragments-check.yml

@@ -24,5 +24,5 @@ jobs:
           git branch -r
           diff=$(git diff origin/${{ github.base_ref }} HEAD --name-only)
           changelog_fragments=$(echo "$diff" | grep "^.changes/unreleased/")
-          echo $diff
+          echo $changelog_fragments