Add more demo

src/content/docs/en/article-components.mdx

@@ -88,6 +88,23 @@ const config: HardhatUserConfig = {
 ...
 ```
 
+```js "return true;" ins="inserted" del="deleted"
+function demo() {
+  console.log('These are inserted and deleted marker types');
+  // The return statement uses the default marker type
+  return true;
+}
+```
+
+```diff lang="js"
+  function thisIsJavaScript() {
+    // This entire block gets highlighted as JavaScript,
+    // and we can still add diff markers to it!
+-   console.log('Old code to be removed')
++   console.log('New and shiny code!')
+  }
+```
+
 Let's see a horizontal rule.
 
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