title: Prevent electron-builder from packaging required node_modules
body: <p>I'm using <code>electron-builder</code> to build my <code>electron</code> application as a desktop app.
  The build was fine, but its size was very large (68Mb).</p>
  
  <p>When I used <code>asar explorer</code> to view my <code>app.asar</code> file. I realize that the <code>app.asar</code> file contains a folder named <code>node_modules</code>, in the <code>node_modules</code>, there are npm folders that have been bundled using <code>webpack</code>, such as: <code>angular</code>, <code>angular-messages</code>, <code>ui-cropper</code>, ...</p>
  
  <p><a href="https://i.stack.imgur.com/VEC6L.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VEC6L.png" alt="List of required folders"></a></p>
  
  <p>How can I ignore those folder from being included in <code>app.asar</code> file ?</p>
  
  <p>They have been bundled by <code>webpack</code> before.</p>
  
  <p>Thank you</p>