Add cache property for select2 ajax options

select2/select2.d.ts

@@ -26,6 +26,7 @@ interface Select2AjaxOptions {
     url?: any;
     dataType?: string;
     quietMillis?: number;
+    cache?: boolean;
     data?: (term: string, page: number, context: any) => any;
     results?: (term: any, page: number, context: any) => any;
 }