add a workaround for bad save button in rtl mode

Bootstrap provides a different set of CSS for RTL languages, but having
to deal with two separate sets of css files depending on the language
would be a PITA.

ts/deckconfig/OptionsDropdown.svelte

@@ -66,7 +66,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     }
 </style>
 
-<div class="btn-group">
+<div class="btn-group" dir="ltr">
     <button
         type="button"
         class="btn btn-primary"