Bug 1578069 - Mirror the reset button on about:config for RTL r=jaws

Differential Revision: https://phabricator.services.mozilla.com/D44316

--HG--
extra : moz-landing-system : lando

browser/components/aboutconfig/content/aboutconfig.css

@@ -180,3 +180,7 @@ td.cell-value > form > input[type="number"] {
 .button-reset {
   background-image: url("chrome://browser/skin/undo.svg");
 }
+
+.button-reset:dir(rtl) {
+  transform: scaleX(-1);
+}