chore: update readme

Author: finkef

README.md

@@ -3,8 +3,12 @@
 ![npm version](https://img.shields.io/npm/v/react-native-tailwind.macro)
 ![github workflow status](https://img.shields.io/github/workflow/status/finkef/react-native-tailwind.macro/ci)
 
+![demo](images/demo.png)
+
 > Babel macro for easily writing responsive Tailwind styles in React Native (+ Web).
 
+---
+
 Easily style components using the `tw` prop:
 
 ```ts