Fix bgcolor of option els when in FF sidebar

src/popup/scss/misc.scss

@@ -338,3 +338,9 @@ input[type="password"]::-ms-reveal {
         }
     }
 }
+
+// Workaround for rendering error in Firefox sidebar when in dark mode
+// option elements will not render background-color correctly if identical to parent background-color
+html.theme_dark select option {
+    background-color: adjust-color(map-get(map-get($themes, dark), inputBackgroundColor), +1);
+}