ci: Add Markdown Links Checker (#119)

.github/workflows/markdown-link-checker.yml

@@ -0,0 +1,16 @@
+name: Markdown Links Checker
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '0 0 * * 0' # weekly run
+jobs:
+  check-links:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: gaurav-nelson/github-action-markdown-link-check@a996638015fbc9ef96beef1a41bbad7df8e06154
+        # checks all markdown files from root but ignores subfolders
+        with:
+          use-quiet-mode: 'yes'
+          use-verbose-mode: 'yes'
+          max-depth: 0