add link-check CI workflow

Author: aspiers

.github/workflows/link-check.yml

@@ -0,0 +1,25 @@
+name: Check for broken links
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  lychee:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Run lychee link checker
+        uses: lycheeverse/[email protected]
+        with:
+          args: >-
+            --verbose
+            --no-progress
+            --exclude-mail
+            **/*.md
+          fail: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}