ci: add markdown linting workflow (#16)

* ci: add markdown linting workflow

* fix: disable MD025 for frontmatter and H1 compatibility

---------

Co-authored-by: gandalf-the-greybeard[bot] <gandalf-the-greybeard[bot]@users.noreply.github.com>

.github/workflows/ci.yaml

@@ -0,0 +1,17 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Lint Markdown
+        uses: DavidAnson/markdownlint-cli2-action@v15
+        with:
+          globs: "**/*.md"

.markdownlint-cli2.jsonc

@@ -0,0 +1,7 @@
+{
+  "config": {
+    "MD013": false, // Disable line length rule as it's often too restrictive for docs
+    "MD041": false, // Disable first-line heading rule (frontmatter often comes first)
+    "MD025": false  // Allow frontmatter title and H1
+  }
+}