Add Smartphone screen favourite back button and adjust styles (#4813)

* Feat add get-back button on favourite columnHeader

* Style adjust nice looking get-back button

* Fix delete media query and add padding right

* fix: restore padding and add lastchild style for back-button

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

@@ -77,6 +77,7 @@ export default class Favourites extends ImmutablePureComponent {
           onClick={this.handleHeaderClick}
           pinned={pinned}
           multiColumn={multiColumn}
+          showBackButton
         />
 
         <StatusList

app/javascript/styles/components.scss

@@ -1622,6 +1622,10 @@
   &:hover {
     text-decoration: underline;
   }
+
+  &:last-child {
+    padding: 0 15px 0 0;
+  }
 }
 
 .column-back-button__icon {