Add Markdown linter GH action (#5762)

.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@v4
+      with:
+        node-version: lts/*
+    - name: Run Markdownlint
+      run: |
+        echo "::add-matcher::.github/workflows/markdownlint-problem-matcher.json"
+        npm i -g markdownlint-cli
+        markdownlint "**/*.md"

.markdownlint.json

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+{
+    "default": true,
+    "MD033": false, // no inline HTML
+
+    // The following rules are disabled to allow the linter to be enabled.
+    // Follow-up work will be done to enable these rules and clean up the violations.
+    "MD001": false, // heading-increment Heading levels should only increment by one level at a time 
+    "MD004": false, // ul-style Unordered list style
+    "MD005": false, // list-indent Inconsistent indentation for list items at the same level
+    "MD007": false, // ul-indent Unordered list indentation
+    "MD009": false, // no-trailing-spaces Trailing spaces
+    "MD010": false, // no-hard-tabs Hard tabs
+    "MD011": false, // no-reversed-links Reversed link syntax
+    "MD012": false, // no-multiple-blanks Multiple consecutive blank lines
+    "MD013": false, // line length
+    "MD014": false, // commands-show-output Dollar signs used before commands without showing output
+    "MD022": false, // blanks-around-headings Headings should be surrounded by blank lines
+    "MD024": false, // no-duplicate-heading Multiple headings with the same content
+    "MD025": false, // single-title/single-h1 Multiple top-level headings in the same document
+    "MD026": false, // no-trailing-punctuation Trailing punctuation in heading
+    "MD028": false, // no-blanks-blockquote Blank line inside blockquote
+    "MD031": false, // blanks-around-fences Fenced code blocks should be surrounded by blank lines
+    "MD032": false, // blanks-around-lists Lists should be surrounded by blank lines
+    "MD034": false, // no-bare-urls Bare URL used
+    "MD036": false, // no-emphasis-as-heading Emphasis used instead of a heading
+    "MD037": false, // no-space-in-emphasis Spaces inside emphasis markers
+    "MD040": false, // fenced-code-language Fenced code blocks should have a language specified 
+    "MD041": false, // first-line-heading/first-line-h1 First line in a file should be a top-level heading
+    "MD047": false, // single-trailing-newline Files should end with a single newline character
+    "MD049": false, // emphasis-style Emphasis style
+    "MD051": false, // link-fragments Link fragments should be valid
+}