[gimp] themes: switch should have a border otherwise it's hard to understand.

[Jehan <jehanp src gnome org>]

commit 4ab1102ae2a4ae4457fa0e109e94c414681f2402
Author: Jehan <jehan girinstud io>
Date:   Thu Sep 29 00:04:12 2022 +0200

    themes: switch should have a border otherwise it's hard to understand.

 themes/Default/common.css | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/themes/Default/common.css b/themes/Default/common.css
index 7a2f160894..a1e5300fc2 100644
--- a/themes/Default/common.css
+++ b/themes/Default/common.css
@@ -389,6 +389,7 @@ list {
 
 switch {
   background-color: @bg-color;
+  border: 1px solid @stronger-border-color;
 }
 
 /* The switch button is quite hard to understand without color IMO. So