refact: Migrate $helper.isUploadEvent to TS (#7985)

Author: distantnative

panel/lab/internals/helpers/isUploadEvent/index.php

@@ -1,5 +1,5 @@
 <?php
 
 return [
-	'source' => 'panel/src/helpers/isUploadEvent.js'
+	'source' => 'panel/src/helpers/isUploadEvent.ts'
 ];

panel/src/helpers/index.js

@@ -7,7 +7,7 @@ import field from "./field.js";
 import file from "./file.js";
 import focus from "./focus.js";
 import isComponent from "./isComponent";
-import isUploadEvent from "./isUploadEvent.js";
+import isUploadEvent from "./isUploadEvent";
 import keyboard from "./keyboard";
 import link from "./link.js";
 import object from "./object.js";

panel/src/helpers/isUploadEvent.js panel/src/helpers/isUploadEvent.tspanel/src/helpers/isUploadEvent.js renamed to panel/src/helpers/isUploadEvent.ts

@@ -1,8 +1,7 @@
 /**
  * Checks if provided event is an upload-related event
- * @returns {bool}
  */
-export default (event) => {
+export default (event: DragEvent): boolean => {
 	if (!event.dataTransfer) {
 		return false;
 	}