Add label-actions workflow

This workflow allows GitHub to automatically act on issue in response to labels
being added to the issue.

.github/workflows/labels.yml

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