[SPARK-49379][FOLLOWUP] Add labler.yml workflow file

### What changes were proposed in this pull request?

This PR aims to add a GitHub Action workflow file, `.github/workflows/.github` too.

### Why are the changes needed?

Previously, we added only mapping file to `.github/labeler.yml` and missed this.
- apache#100

### Does this PR introduce _any_ user-facing change?

No. This is an infra PR.

### How was this patch tested?

Manual review.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#102 from dongjoon-hyun/SPARK-49379-2.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

.github/workflows/labeler.yml

@@ -0,0 +1,40 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+# Intentionally has a general name.
+# because the test status check created in GitHub Actions
+# currently randomly picks any associated workflow.
+# So, the name was changed to make sense in that context too.
+# See also https://github.community/t/specify-check-suite-when-creating-a-checkrun/118380/10
+
+name: "On pull requests"
+on: pull_request_target
+
+jobs:
+  label:
+    name: Label pull requests
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+    - uses: actions/labeler@v5
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"
+        sync-labels: true