Enable the pulsarbot action to react comments (apache#6223)

*Motivation*

A `pulsarbot` action was added to pulsar-test-infra for processing comments and trigger running github actions.

This pull request is to enable this action to process comments.

.github/workflows/ci-pulsarbot.yaml

@@ -0,0 +1,37 @@
+#
+# 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.
+#
+
+name: Pulsar Bot
+on:
+  issue_comment:
+    types: [created]
+
+jobs:
+
+  action-runner:
+    name:
+    runs-on: ubuntu-latest
+    timeout-minutes: 120
+
+    steps:
+      - name: checkout
+        uses: actions/checkout@v1
+      - name: Execute pulsarbot command
+        id:   pulsarbot
+        uses: apache/pulsar-test-infra/pulsarbot@master