Update README.md

Author: WittBulter

README.md

@@ -1,8 +1,9 @@
+<br>
 <div align="center" height="500">
-<img src="logo.png" width="350" height="220" align="center">
+<img src="logo.png" width="460" height="220" align="center">
 </div>
 
-<br><br>
+<br><br><br>
 ### back-loader
 > a easy and steady preload lib, you can use it to load all kinds of resources. use **back-loader** in your project,
 > can quickly preload more pictures, styles(.css) or scripts, it will make your website more fluent.
@@ -17,17 +18,24 @@
 import { BackLoader } from 'back-loader'
 
 const backHandler = new BackLoader({
-  urls: string[],
-  scripts: string[],
-  styles: string[],
-  images: string[],
+  urls?: string[],
+  scripts?: string[],
+  styles?: string[],
+  images?: string[],
 })
 
 // at the right time:
 backHandler.start()
-backHandler.onload = (event: any) => {
+backHandler.onload = (event: loadEvent) => {
   console.log(event)
 }
+
+type loadEvent = {
+  source: string,           // resource url, like: 'host.com/a.js'
+  type: string,             // resource type, like: 'script' / 'style' / 'image'
+  success: boolean,
+  insertScripts?: Function,
+}
 ```
 
 #### LICENSE