doc: Update README.md

README.md

@@ -28,13 +28,27 @@ CDN: [UNPKG](https://unpkg.com/@wcj/dark-mode/dist/) | [jsDelivr](https://cdn.js
 
 There are two ways how you can use `<dark-mode>`:
 
-
 ```html
 <dark-mode></dark-mode>
 <dark-mode light="Dart" dark="Light"></dark-mode>
 <dark-mode dark="Dark" light="Light" style="border: 1px solid red; font-size: 12px;"></dark-mode>
 ```
 
+Use in [React](https://github.com/facebook/react):
+
+```jsx
+import React from 'react';
+import '@wcj/dark-mode';
+
+function Demo() {
+  return (
+    <div>
+      <dark-mode light="Dart" dark="Light"></dark-mode>
+    </div>
+  );
+}
+```
+
 ## Contributors
 
 As always, thanks to our amazing contributors!