Use markdownlint GitHub action (#1507)

.github/workflows/markdownlint-problem-matcher.json

@@ -0,0 +1,17 @@
+{
+    "problemMatcher": [
+        {
+            "owner": "markdownlint",
+            "pattern": [
+                {
+                    "regexp": "^([^:]*):(\\d+):?(\\d+)?\\s([\\w-\\/]*)\\s(.*)$",
+                    "file": 1,
+                    "line": 2,
+                    "column": 3,
+                    "code": 4,
+                    "message": 5
+                }
+            ]
+        }
+    ]
+}

.github/workflows/markdownlint.yml

@@ -0,0 +1,29 @@
+name: Markdownlint
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+    paths:
+      - "**/*.md"
+      - ".markdownlint.json"
+      - ".github/workflows/markdownlint.yml"
+      - ".github/workflows/markdownlint-problem-matcher.json"
+
+jobs:
+  lint:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use Node.js
+      uses: actions/setup-node@v1
+      with:
+        node-version: 16.x
+    - name: Run Markdownlint
+      run: |
+        echo "::add-matcher::.github/workflows/markdownlint-problem-matcher.json"
+        npm i -g markdownlint-cli
+        markdownlint "**/*.md"

.markdownlint.json

@@ -1,5 +1,8 @@
 {
     "default": true,
+    "MD009": {
+      "br_spaces": 0
+    },
     "MD013": false,
     "MD046": {
       "style": "fenced"

azure-pipelines.yml

@@ -14,8 +14,10 @@ pr:
     exclude:
       - .github/*
       - .devcontainer/*
-      - CODE-OF-CONDUCT.md
-      - LICENSE
+      - docs/*
+      - CODE_OF_CONDUCT.md
+      - CONTRIBUTING.md
+      - README.md
       - SECURITY.md
 
 parameters:
@@ -234,13 +236,3 @@ stages:
         SkipLocProjectJsonGeneration: true
         GitHubOrg: microsoft
         MirrorRepo: testfx
-
-  - ${{ if eq(variables._RunAsPublic, True) }}:
-    - job: Markdownlint
-      pool:
-          vmImage: ubuntu-22.04
-      steps:
-        - script: sudo npm install -g markdownlint-cli@0.32.2
-          displayName: Install markdownlint-cli
-        - script: markdownlint '**/*.md'
-          displayName: Run markdownlint