Move style code to CSS

src/components/layers/LayerEditorGroup.jsx

@@ -36,18 +36,7 @@ export default class LayerEditorGroup extends React.Component {
 
   render() {
     return <div>
-      <div style={{
-        fontWeight: 'bold',
-        fontSize: fontSizes[4],
-        backgroundColor: this.state.hover ? Color(colors.black).lighten(0.30).string() : Color(colors.black).lighten(0.15).string(),
-        color: colors.lowgray,
-        cursor: 'pointer',
-        userSelect: 'none',
-        padding: margins[1],
-        display: 'flex',
-        flexDirection: 'row',
-        lineHeight: '20px',
-      }}
+      <div className="maputnik-layer-editor-group"
         onMouseOver={e => this.setState({hover: true})}
         onMouseOut={e => this.setState({hover: false})}
         onClick={e => this.props.onActiveToggle(!this.props.isActive)}