Add Author Feedback label automatically (#28484)

Summary:
Improve issue triage by automatically adding the "Needs: Author Feedback" label.

NOTE: The old label-actions app should be disabled when this PR is merged: https://github.com/apps/label-actions/installations/7445225

## Changelog

[Internal] - Issue Triage
Pull Request resolved: https://github.com/facebook/react-native/pull/28484

Test Plan: Verified the same `label-actions.yml` and workflow config on a private repo.

Reviewed By: cpojer

Differential Revision: D20817443

Pulled By: hramos

fbshipit-source-id: 39732dd67509c9fb9cf6ff7306913f5ec088266d

.github/workflows/process-label-actions.yml

@@ -0,0 +1,16 @@
+name: Label Actions
+# This workflow is triggered when a label is added to an issue.
+on:
+  issues:
+    types: labeled
+
+jobs:
+  processLabelAction:
+    name: Process Label Action
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Process Label Action
+        uses: hramos/label-actions@v1
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}