Add lychee-action workflow for automated link checking

Created GitHub Action workflow using lychee-action to detect broken links:
- check-links.yml: Runs on push to main and on pull requests
- Scans content/**/*.{md,mdx}, docs/**/*.{md,mdx}, and README.md
- Fails CI if broken links are found
- .lycheeignore: Ignores localhost, example.com, and social media links

This provides an additional layer of link validation alongside the existing
custom validation script.

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

.github/workflows/check-links.yml

@@ -0,0 +1,33 @@
+name: Check Links
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  check-links:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Check links with Lychee
+        uses: lycheeverse/lychee-action@v1
+        with:
+          # Scan all markdown files in content directories and README
+          args: |
+            --verbose
+            --no-progress
+            --exclude-path .git
+            --exclude-path node_modules
+            'content/**/*.md'
+            'content/**/*.mdx'
+            'docs/**/*.md'
+            'docs/**/*.mdx'
+            'README.md'
+          # Fail the action on broken links
+          fail: true
+        env:
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}

.lycheeignore

@@ -0,0 +1,9 @@
+# Ignore localhost links (development/testing)
+http://localhost*
+
+# Ignore example links
+https://example.com
+
+# Ignore social media links (anti-scraping measures)
+https://twitter.com*
+https://x.com*