Introduce link checker job

.github/workflows/linkcheck.yml

@@ -0,0 +1,21 @@
+name: Link checker
+
+on: push
+
+#env:
+#  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+#
+jobs:
+  build:
+    name: Build and Test
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - uses: gaurav-nelson/github-action-markdown-link-check@v1
+        with:
+          config-file: 'mlc_config.json'
+          folder-path: 'docs' # comma separated
+          max-depth: 2
+          # check-modified-files-only: ${{ github.event_name == 'pull_request' && 'yes' || 'no' }}
+          base-branch: main