Mayland: Add config-separator.width default variable.

mayland/sass/_config-child-theme-deep.scss

@@ -279,6 +279,7 @@ $config-quote: (
 
 $config-separator: (
 	"height": #{0.25 * $baseline-unit},
+	"width": #{6 * map-deep-get($config-global, "spacing", "horizontal")},
 );
 
 /**