Fix the SCSS global variable warnings (#269)

- fix the scss version 2 warning that global variables need to be declared at the root

Author: madoar

src/css/archwizard.scss

@@ -141,6 +141,10 @@ $aw-distance-between-steps: 10px !default;
 
 $aw-text-height: 14px !default;
 
+// declare global variables
+$aw-param-indicator-width: null;
+$aw-param-indicator-height: null;
+$aw-param-indicator-border-width: null;
 
 aw-wizard {
   display: flex;