Add scrollbars to editors

styles/src/styleTree/editor.ts

@@ -1,4 +1,5 @@
 import Theme from "../themes/common/theme";
+import { withOpacity } from "../utils/color";
 import {
   backgroundColor,
   border,
@@ -170,6 +171,19 @@ export default function editor(theme: Theme) {
         background: backgroundColor(theme, "on500"),
       },
     },
+    scrollbar: {
+      width: 12,
+      track: {
+        border: {
+          left: true,
+          width: 1,
+          color: borderColor(theme, "secondary"),
+        },
+      },
+      thumb: {
+        background: borderColor(theme, "secondary"),
+      }
+    },
     compositionMark: {
       underline: {
         thickness: 1.0,