add extra classes for styling purposes

Author: Ghislain Beaulac

src/app/modules/angular-slickgrid/formatters/checkmarkFormatter.ts

@@ -1,4 +1,4 @@
 import { Formatter } from './../models/formatter.interface';
 
 export const checkmarkFormatter: Formatter = (row: number, cell: number, value: any, columnDef: any, dataContext: any) =>
-  value ? `<i class="fa fa-check" aria-hidden="true"></i>` : '';
+  value ? `<i class="fa fa-check checkmark-icon" aria-hidden="true"></i>` : '';