[libshumate] license: Improve readability

[Marcus Lundblad <mlundblad src gnome org>]

commit c5a0fa606622852962c513c3bcc0096e9933eda6
Author: James Westman <james jwestman net>
Date:   Fri Jun 4 12:54:41 2021 -0500

    license: Improve readability
    
    Add a translucent background to the license so it's easier to read,
    especially on dark themes with light text color.

 data/license.css | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/data/license.css b/data/license.css
index 8ffe647..4aa6b67 100644
--- a/data/license.css
+++ b/data/license.css
@@ -1,6 +1,8 @@
 map-license label {
   font-size: x-small;
-  opacity: 0.8;
+  background: alpha(@theme_bg_color, 0.5);
+  border-radius: 3px;
+  padding: 3px;
 }
 
 map-license {