[gnome-games] style: Add style for favorite star image

[Alexander Mikhaylenko <alexm src gnome org>]

commit e633522bb2d4dda6a9fd3ecaffe06305d752d8ca
Author: Neville <nevilleantony98 gmail com>
Date:   Thu Jun 18 22:07:55 2020 +0530

    style: Add style for favorite star image
    
    Adds 1px black border for better contrast on some covers.
    Sets margins for a better position of stars on covers.

 data/gtk-style.css | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/data/gtk-style.css b/data/gtk-style.css
index 988605db..32608467 100644
--- a/data/gtk-style.css
+++ b/data/gtk-style.css
@@ -1,5 +1,15 @@
 /* This file is part of GNOME Games. License: GPL-3.0+. */
 
+.favorite-star {
+       color: white;
+       -gtk-icon-shadow: 0 1px black, 0 -1px black, 1px 0 black, -1px 0 black;
+       margin: 6px;
+}
+
+.hide-stars .favorite-star {
+       opacity: 0;
+}
+
 .snapshot-row {
        padding: 0;
 }