Updated Settings (markdown)

Settings.md

@@ -33,6 +33,14 @@ and then reference that image:
 background: /images/background.png
 ```
 
+### Background Opacity
+
+You can change the opacity of the background, to blend it with the primary theme color,
+
+```yaml
+backgroundOpacity: 0.5
+```
+
 ## Favicon
 
 If you'd like to use a custom favicon instead of the included one, you may provide a full URL to an image of your choice.