[gnome-builder] help: update styling for code

[Christian Hergert <chergert src gnome org>]

commit 38e263f849555cce6208192a1eb8968013962646
Author: Christian Hergert <chergert redhat com>
Date:   Tue Mar 12 14:47:16 2019 -0700

    help: update styling for code

 doc/help/_static/theme_overrides.css | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/doc/help/_static/theme_overrides.css b/doc/help/_static/theme_overrides.css
index f41e5e60f..fb055f288 100644
--- a/doc/help/_static/theme_overrides.css
+++ b/doc/help/_static/theme_overrides.css
@@ -49,6 +49,10 @@ p {
   color: #333333;
 }
 
+.highlight  {
+  background: #4e9a0633;
+}
+
 .linenos .linenodiv pre,
 .highlight pre {
   font-family: "Source Code Pro", monospace;