fix: 🐛 export createObserver

Author: zWingz

src/index.ts

@@ -1,8 +1,10 @@
 import Image from './lib/Image'
 import Preview, { PreviewApi } from './lib/ImgPreview'
+import { createObserver } from './lib/Image/observer'
 import './style/global.scss'
 export {
   Image,
   Preview,
-  PreviewApi
+  PreviewApi,
+  createObserver
 }