fix formatting and types

types/xlsx/index.d.ts

@@ -254,7 +254,8 @@ export interface IRange {
 
 export interface IUtils {
     /** converts an array of arrays of JS data to a worksheet. */
-	aoa_to_sheet<T>(data:Array, opts?:any);
+    aoa_to_sheet(data: <T>, opts?:any): IWorkSheet;
+
     /** Converts a worksheet object to an array of JSON objects */
     sheet_to_json<T>(worksheet:IWorkSheet, opts?: {
         raw?: boolean;