Handle global hotkeys even when no element has focus (#8998)

This fixes hotkeys not working when pressing the column
“back” button, for instance.

app/javascript/mastodon/features/ui/index.js

@@ -460,7 +460,7 @@ class UI extends React.PureComponent {
     };
 
     return (
-      <HotKeys keyMap={keyMap} handlers={handlers} ref={this.setHotkeysRef}>
+      <HotKeys keyMap={keyMap} handlers={handlers} ref={this.setHotkeysRef} attach={window} focused>
         <div className={classNames('ui', { 'is-composing': isComposing })} ref={this.setRef} style={{ pointerEvents: dropdownMenuIsOpen ? 'none' : null }}>
           <TabsBar />