Add firstpos1 and firstpos2 properties to PNotify stack

Per PNotify documentation:
https://github.com/sciactive/pnotify#example-stacks

jquery.pnotify/jquery.pnotify.d.ts

@@ -11,6 +11,8 @@ interface PNotifyStack {
     push?: string;
     spacing1?: number;
     spacing2?: number;
+    firstpos1?: number;
+    firstpos2?: number;
     context?: JQuery
 }