Use monospace font for regex in searchable

Summary:
Seemed a bit weird typing a regex without monospace.
Still would be good to have syntax highlighting. I tried using prismjs, but it seems to not work by default on Input elements.

Reviewed By: danielbuechele

Differential Revision: D15918742

fbshipit-source-id: b44c228b30f37f97811d09c80b191b52282720f8

src/ui/components/searchable/Searchable.js

@@ -37,6 +37,7 @@ export const SearchBox = styled(FlexBox)({
 
 export const SearchInput = styled(Input)(props => ({
   border: props.focus ? '1px solid black' : 0,
+  ...(props.regex ? {fontFamily: 'monospace'} : {}),
   padding: 0,
   fontSize: '1em',
   flexGrow: 1,
@@ -437,6 +438,7 @@ const Searchable = (
                   ? this.state.compiledRegex !== null
                   : true
               }
+              regex={this.state.regexEnabled && this.state.searchTerm}
             />
           </SearchBox>
           {this.props.regexSupported ? (