title: Browsersync no server using Roots Sage
body: <p>I'm trying to develop a Wordpress Theme with Wordpress and Roots Sage.
  In my Theme folder i installed sage with</p>
  
  <pre><code>composer create-project roots/sage my-theme
  </code></pre>
  
  <p>After i entered all configuration I tried to start the development build with <code>yarn start</code> which invokes <code>webpack --hide-modules --watch --config resources/assets/build/webpack.config.js</code>.</p>
  
  <p>Browsersync then gives me:</p>
  
  <pre><code>[BS] [HTML Injector] Running...
  [Browsersync] Proxying: http://test.local
  [Browsersync] Access URLs:
   ----------------------------------------
         Local: http://localhost:3000
      External: http://xxx:3000
   ----------------------------------------
            UI: http://localhost:3001
   UI External: http://xxx:3001
   ----------------------------------------
  [Browsersync] Watching files...
  </code></pre>
  
  <p>A browsertab opens, however there is no response in any form. The page just keeps loading.</p>
  
  <p>Webpack config (<code>resources/assets/build/webpack.config.js</code>) is</p>
  
  <pre><code>{
    "entry": {
      "main": [
        "./scripts/main.js",
        "./styles/main.scss"
      ],
      "customizer": [
        "./scripts/customizer.js"
      ]
    },
    "publicPath": "/wp-content/themes/my-theme",
    "devUrl": "http://test.local",
    "proxyUrl": "http://localhost:3000",
    "cacheBusting": "[name]_[hash:8]",
    "watch": [
      "app/**/*.php",
      "config/**/*.php",
      "resources/views/**/*.php"
    ]
  }
  </code></pre>
  
  <p>Any ideas?
  Thanks!</p>