My error

index.js

import React from "react";
import { render } from "react-dom";

class App extends React.Component {
  render() {
    return {
      <div>
        <h1>Hello!</h1>
      </div>
    };
  }
}

render(<App/>, window.document.getElementById('app'));

package.json

{
  "name": "bliimo-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "npm run build",
    "build": "webpack -d && copy src\\index.html dist\\index.html && webpack-dev-server --content-base src\\ --inline --hot",
    "build:prod": "webpack -p && copy src/index.html dist/index.html"
  },
  "author": "Jeff Ramirez",
  "license": "ISC",
  "dependencies": {
    "react": "^15.6.1",
    "react-dom": "^15.6.1"
  },
  "devDependencies": {
    "babel-core": "^6.26.0",
    "babel-loader": "^7.1.2",
    "babel-preset-env": "^1.6.0",
    "babel-preset-es2015": "^6.24.1",
    "babel-preset-react": "^6.24.1",
    "babel-preset-stage-2": "^6.24.1",
    "webpack": "^3.6.0",
    "webpack-dev-server": "^2.8.2"
  }
}

webpack.config.js

var webpack = require("webpack");
var path = require("path");

var DIST_DIR = path.resolve(__dirname, "dist");
var SRC_DIR = path.resolve(__dirname, "src");

var config = {
  entry: SRC_DIR + "/app/index.js",
  output: {
    path: DIST_DIR + "/app",
    filename: "bundle.js",
    publicPath: "/app"
  },
  module: {
    loaders: [
      {
        test: /\.js?/,
        include: SRC_DIR,
        loader: "babel-loader",
        query: {
          presets: ["react", "env"]
        }
      }
    ]
  }
};

module.exports = config;