Add workflow to check for broken links

.github/workflows/link-check.yml

@@ -0,0 +1,36 @@
+name: Link Check
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: "${{ github.workflow }}-${{ github.ref }}"
+  cancel-in-progress: true
+
+jobs:
+  link-check:
+    name: Check links
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - name: Check links
+        uses: lycheeverse/lychee-action@v2
+        with:
+          # The offline check makes no API calls, so it needs no token
+          token: ""
+          # --offline blocks network requests so only internal links are checked.
+          # --root-dir is needed for docsify's root-relative links such as /plugin-dev.md
+          args: --offline --root-dir "$(pwd)" --include-fragments --no-progress './**/*.md'
+          fail: true
+          jobSummary: true