Add useTheme to the list of native exports (#2982)

* Add useTheme to the default export

* Update CHANGELOG.md

Co-authored-by: Evan Jacobs <probablyup@gmail.com>

CHANGELOG.md

@@ -6,6 +6,8 @@ _The format is based on [Keep a Changelog](http://keepachangelog.com/) and this
 
 ## Unreleased
 
+- Added useTheme hook to named exports for react native  
+
 ## [v5.0.0] - 2020-01-13
 
 Read the [v5 release announcement](https://medium.com/styled-components/announcing-styled-components-v5-beast-mode-389747abd987)!

packages/styled-components/src/native/index.js

@@ -8,6 +8,7 @@ import css from '../constructors/css';
 import constructWithOptions from '../constructors/constructWithOptions';
 import ThemeProvider, { ThemeConsumer, ThemeContext } from '../models/ThemeProvider';
 import withTheme from '../hoc/withTheme';
+import useTheme from '../hooks/useTheme';
 import isStyledComponent from '../utils/isStyledComponent';
 
 import type { Target } from '../types';
@@ -40,5 +41,5 @@ aliases.split(/\s+/m).forEach(alias =>
   })
 );
 
-export { css, isStyledComponent, ThemeProvider, ThemeConsumer, ThemeContext, withTheme };
+export { css, isStyledComponent, ThemeProvider, ThemeConsumer, ThemeContext, withTheme, useTheme };
 export default styled;