add markdown linter

.github/workflows/md-link.yaml

@@ -0,0 +1,14 @@
+on:
+  pull_request:
+    branches:
+      - main
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: DavidAnson/markdownlint-cli2-action@v15
+      continue-on-error: true
+      with:
+        globs: |
+          docs/*.md