simplify import

Author: trusktr

src/core/index.js

@@ -1,8 +1,8 @@
-import * as dom from './util/dom';
+import { documentReady } from './util/dom';
 import { Docsify } from './Docsify';
 
 /**
  * Run Docsify
  */
 // eslint-disable-next-line no-unused-vars
-dom.documentReady(_ => new Docsify());
+documentReady(_ => new Docsify());