test(CHANGELOG): add GH action step summaries from check

Author: ErichDonGubler

.github/workflows/changelog.yml

@@ -39,4 +39,4 @@ jobs:
 
       - name: Run `cargo xtask changelog …`
         run: |
-          cargo xtask changelog --emit-github-messages "origin/${{ github.event.pull_request.base.ref }}"
+          cargo --quiet xtask changelog --emit-github-messages "origin/${{ github.event.pull_request.base.ref }}" 2> >(tee --append "$GITHUB_STEP_SUMMARY" >&2)