fix: react-dropdown width

Author: yuhsuanchuang

packages/react-dropdown/src/Categories.js

@@ -46,6 +46,7 @@ const Category = styled.main`
   display: flex;
   flex-direction: ${props => (props.twoColumn ? 'row' : 'column')};
   flex-grow: 1;
+  width: 100%;
 `;
 
 export const Divider = styled.section`

packages/react-dropdown/src/Items.js

@@ -41,6 +41,7 @@ const Items = styled.ul`
   display: flex;
   flex-direction: column;
   flex-grow: 1;
+  width: 100%;
 `;
 
 export const HIGHLIGHTED = (props: { theme: Object }) =>