remove unnecessary _init call

Author: trusktr

src/core/Docsify.js

@@ -16,12 +16,7 @@ export class Docsify extends multiple(
   renderMixin,
   fetchMixin,
   eventMixin
-) {
-  constructor() {
-    super();
-    this._init();
-  }
-}
+) {}
 
 /**
  * Global API

src/core/init/index.js

@@ -2,7 +2,9 @@ import config from '../config';
 
 export function initMixin(Base = class {}) {
   return class extends Base {
-    _init() {
+    constructor() {
+      super();
+
       this.config = config(this);
 
       this.initLifecycle(); // Init hooks