update client/less/main.less

- add btn-default hover background color

client/less/main.less

@@ -1155,6 +1155,12 @@ code {
   }
 }
 
+// make btn-default hover more visible
+.btn-default:active,
+.btn-default:hover {
+    background-color: @brand-primary;
+}
+
 @import "chat.less";
 @import "jobs.less";
 @import "challenge.less";