[gtk/wip/baedert/for-master: 50/50] gtk4-demo: Add background to CSS Basics demo

[Timm Bäder <baedert src gnome org>]

commit 5534d3fc829c52e41d8791fcbe557c251ac8fbf0
Author: Timm Bäder <mail baedert org>
Date:   Sat Aug 8 21:11:38 2020 +0200

    gtk4-demo: Add background to CSS Basics demo
    
    So people can at least read the textview contents

 demos/gtk-demo/css_basics.css | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/demos/gtk-demo/css_basics.css b/demos/gtk-demo/css_basics.css
index 0b3365f50f..238ad46667 100644
--- a/demos/gtk-demo/css_basics.css
+++ b/demos/gtk-demo/css_basics.css
@@ -15,6 +15,10 @@
   border: 1px solid;
 }
 
+window {
+  background-color: white;
+}
+
 /* Make sure selections are visible */
 selection {
   background-color: darkGreen;