Add link checker workflow to validate markdown links

.gitea/workflows/link-checker.yml

@@ -0,0 +1,20 @@
+name: Check Links
+
+on:
+  push:
+  
+jobs:
+  lycheee:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v4
+
+      - name: Link Checker
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: --verbose --no-progress './**/*.md'
+          # Fail the build if broken links are found
+          fail: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}