improve sidebar on small screen

src/Sidebar.js

@@ -16,7 +16,7 @@ export class Sidebar extends PureComponent {
     render() {
         return (
             <div className={this.props.title!==null ? 'sidebar-on' : ''}>
-                <div className="sidebar-shadow" onClick={this.props.do_close} />
+                <div className="sidebar-shadow" onClick={this.props.do_close} onTouchEnd={(e)=>{e.preventDefault();e.target.click();}} />
                 <div ref={this.sidebar_ref} className="sidebar">
                     {this.props.content}
                 </div>