docs: fix the broken image url (#767)

Author: chenxsan

README.md

@@ -1,5 +1,5 @@
 <div align="center">
-  <img width="200" height="200" src="https://cdn.worldvectorlogo.com/logos/javascript.svg">
+  <img width="200" height="200" src="https://cdn.worldvectorlogo.com/logos/logo-javascript.svg">
   <a href="https://webpack.js.org/">
     <img width="200" height="200" vspace="" hspace="25" src="https://cdn.rawgit.com/webpack/media/e7485eb2/logo/icon-square-big.svg">
   </a>