feat: Add prettier enforcement (apache#2783)

Author: andygrove

.github/workflows/pr_markdown_format.yml

@@ -0,0 +1,49 @@
+# 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: Check Markdown Formatting
+
+concurrency:
+  group: ${{ github.repository }}-${{ github.head_ref || github.sha }}-${{ github.workflow }}
+  cancel-in-progress: true
+
+on:
+  pull_request:
+    paths:
+      - '**.md'
+
+jobs:
+  prettier-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: '24'
+
+      - name: Install prettier
+        run: npm install -g prettier
+
+      - name: Check markdown formatting
+        run: |
+          # if you encounter error, run prettier locally and commit changes using instructions at:
+          #
+          # https://datafusion.apache.org/comet/contributor-guide/development.html#how-to-format-md-document
+          #
+          prettier --check "**/*.md"