ci: add markdownlint-cli2-action@v11

.github/workflows/markdownlint.yml

@@ -0,0 +1,24 @@
+name: markdownlint
+on: [push, pull_request]
+jobs:
+  markdownlint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 2
+
+      - name: Get Changed Files
+        id: changed-files
+        uses: tj-actions/changed-files@v38
+        with:
+          files: '**/*.md'
+          separator: ','
+
+      - name: Lint Markdown Documents
+        uses: DavidAnson/markdownlint-cli2-action@v11
+        if: steps.changed-files.outputs.any_changed == 'true'
+        with:
+          globs: ${{ steps.changed-files.outputs.all_changed_files }}
+          separator: ','