publish react-tree core package (#27)

* publish react-tree core package

* fix snapshot

Author: liorheber

packages/core/src/index.js

@@ -1,5 +1,5 @@
 import React from "react";
 
-const HelloWorld = () => <div>HelloWorld</div>;
+const HelloWorld = () => <div>Hello World</div>;
 
 export default HelloWorld;

packages/core/tests/__snapshots__/index.spec.js.snap

@@ -2,6 +2,6 @@
 
 exports[`core component will render 1`] = `
 <div>
-  HelloWorld
+  Hello World
 </div>
 `;