.github: Add markdown linter

Signed-off-by: Joe Stringer <[email protected]>

Author: joestringer

.github/workflows/lint.yaml

@@ -0,0 +1,16 @@
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: DavidAnson/markdownlint-cli2-action@v17
+      with:
+        globs: |
+          **/*.md
+          !vendor/**/*.md

.markdownlint.yml

@@ -0,0 +1,5 @@
+default: true
+
+MD002: false # First header should be a h1 header
+MD013: false # Line length
+MD041: false # First line in file should be a top level header