Add Backport PR success comment PR link

Adds a direct link (as a comment) to the new backported PR

.github/actions/backport/action.yml

@@ -62,6 +62,15 @@ runs:
       env:
         GH_TOKEN: ${{ inputs.GITHUB_TOKEN }}
 
+    - name: Report success
+      shell: ${{ env.shell }}
+      run: |
+        gh pr comment "${{ github.event.pull_request.number }}" \
+          --repo ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY} \
+          --body "👍 Created $(gh pr view --json url --jq .url) to backport into [\`${{ inputs.TARGET_BRANCH }}\`](${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/tree/${{ inputs.TARGET_BRANCH }})."
+      env:
+        GH_TOKEN: ${{ inputs.GITHUB_TOKEN }
+
     - name: Report errors
       shell: ${{ env.shell }}
       if: failure() && steps.assert-branch-exists.outputs.failure-already-reported != 'true'