Use markdownlint in CI

.github/workflows/cd.yml

@@ -64,6 +64,25 @@ jobs:
       uses: actions/deploy-pages@v2
 
 
+  markdown-lint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: "Install markdownlint-cli2"
+      run: npm install -g markdownlint-cli2
+
+    - name: "Run lint"
+      run: ./lint.sh
+
+    # Disabled because behavior differs slightly from markdownlint (cli)
+#    - name: "Run lint"
+#      uses: docker://avtodev/markdown-lint:v1 # fastest way; alternative: avto-dev/markdown-lint@v1
+#      with:
+#        args: ReadMe.md "src/**/*.md"
+#        config: .github/other/.markdownlint.jsonc
+
+
   license-guard:
     runs-on: ubuntu-20.04
     steps: