Added buttons to join/leave organisations (no functionality yet)

locale/en_US/messages.php

@@ -110,8 +110,10 @@ return [
 
     'VIEW_DELETED'                       => 'View deleted',
     'DELETED'                            => 'Deleted',
-
     'RETURN'                             => 'Return',
+    
+    'JOIN'                               => 'Join',
+    'LEAVE'                              => 'Leave',
 
     'ACTION_CANNOT_UNDONE'               => 'This action cannot be undone!',
 ];