Context menu loading fixes

- Padding to center loader
- Correcting missing import for `Loader`

src/js/components/ContextMenu/PlaylistSubmenu.js

@@ -3,6 +3,7 @@ import { useDispatch } from 'react-redux';
 import { compact } from 'lodash';
 import { I18n } from '../../locale';
 import Link from '../Link';
+import Loader from '../Loader';
 import Icon from '../Icon';
 import { encodeUri } from '../../util/format';
 import {

src/scss/components/_context-menu.scss

@@ -106,7 +106,8 @@
 		}
 
 		&--loader {
-			padding-top: 75%;
+			text-align: center;
+			margin-top: 50%;
 		}
 	}