docs: adding example in readme

packages/babel-preset-react-app/README.md

@@ -24,10 +24,27 @@ npm install babel-preset-react-app --save-dev
 
 Then create a file named `.babelrc` with following contents in the root folder of your project:
 
-  ```js
-  {
-    "presets": ["react-app"]
-  }
-  ```
+```js
+{
+  "presets": ["react-app"]
+}
+```
 
 This preset uses the `useBuiltIns` option with [transform-object-rest-spread](http://babeljs.io/docs/plugins/transform-object-rest-spread/) and [transform-react-jsx](http://babeljs.io/docs/plugins/transform-react-jsx/), which assumes that `Object.assign` is available or polyfilled.
+
+## Usage with TypeScript
+
+To use this package with [`@babel/preset-typescript`](https://www.npmjs.com/package/@babel/preset-typescript), you need to disable `@babel/preset-flow` first.
+
+You can achieve this by doing:
+
+```
+{
+  "presets": [
+    ["react-app", {
+        "flow": false
+    }],
+    "@babel/typescript"
+  ]
+}
+```