Add LinkSpector

Author: ralfhandl

.github/workflows/validate-markdown.yaml

@@ -20,11 +20,17 @@ jobs:
       - uses: actions/checkout@v5 # checkout repo content
         with:
           fetch-depth: 0
-      # - name: use the javascript environment from main
-      #   run: |
-      #     git checkout remotes/origin/main -- package.json package-lock.json .markdownlint.yaml
+
       - uses: actions/setup-node@v6 # setup Node.js
         with:
           node-version: "22.x"
+
       - name: Lint markdown
         run: npx --yes markdownlint-cli2 --config .markdownlint.yaml npx markdownlint-cli2 *.md schemas/**/*.md versions/*.md
+
+      - name: Check links in markdown files
+        uses: umbrelladocs/action-linkspector@v1
+        with:
+          reporter: github-check
+          fail_level: any
+          filter_mode: file

.linkspector.yml

@@ -0,0 +1,3 @@
+dirs:
+  - ./
+useGitIgnore: true