ci: add pr-labeler

Signed-off-by: Shaun Thompson <shaun.thompson@docker.com>

.github/workflows/labeler.yml

@@ -0,0 +1,19 @@
+name: labeler
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+on:
+  pull_request_target:
+
+jobs:
+  labeler:
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Run
+        uses: actions/labeler@v5