add check

.github/workflows/build-site.yml

@@ -33,10 +33,19 @@ jobs:
     - name: look for todos
       run: "! grep -i -P '<pre\\s*>|TODO|[?]{3,}' */*.md"
 
+  linux3:
+    name: Look for code not highlighted
+    runs-on: ubuntu-latest
+    steps:
+    - name: checkout code
+      uses: actions/checkout@v2.3.1
+    - name: look for unhighlighted code
+      run: "! grep -Pz '\\n\\n```\\n' */*.md"
+
   linux3:
     name: Deploy website
     runs-on: ubuntu-latest
-    needs: [linux1, linux2]
+    needs: [linux1, linux2, linux3]
     if: github.ref == 'refs/heads/master'
     steps:
     - name: update package database