feat(core): setting output var in send email service task

GH-9

Author: maninder-pal-singh

projects/workflows-creator/src/lib/services/bpmn/elements/tasks/send-email.task.ts

@@ -54,7 +54,8 @@ export class SendEmail extends ServiceTaskElement {
       },
     },
   };
-  outputs: string;
+
+  outputs = 'outputVariable';
   static identifier = 'SendEmail';
 
   getIdentifier(): string {