title: Share Assets between frontend and backend in Yii2 Advanced template
body: <p>i've been trying to load a simple CSS (custom.css) from the frontend and backend of my project and I't has been a real pain. </p>
  
  <p>The css is located in:</p>
  
  <pre><code>    frontend/views/web/css/custom.css
  </code></pre>
  
  <p>It loads without problems in the frontend... this is the AppAsset file located in the frontend:</p>
  
  <pre><code>&lt;?php
  
  namespace frontend\assets;
  
  use yii\web\AssetBundle;
  
  /**
   * Main frontend application asset bundle.
   */
  class AppAsset extends AssetBundle
  {
      public $basePath = '@webroot';
      public $baseUrl = '@web';
      public $css = [
          'css/site.css',
          'css/custom.css',
      ];
      public $js = [
      ];
      public $depends = [
          'yii\web\YiiAsset',
          'yii\bootstrap\BootstrapAsset',
      ];
  }
  </code></pre>
  
  <p>So I just thought that the AppAsset file located in backend should look like this:</p>
  
  <pre><code>    &lt;?php
  
  namespace frontend\assets;
  
  use yii\web\AssetBundle;
  
  /**
   * Main backend application asset bundle.
   */
  class AppAsset extends AssetBundle
  {
      public $basePath = '@webroot';
      public $baseUrl = '@web';
      public $css = [
          'css/custom.css',
      ];
      public $js = [
      ];
      public $depends = [
          'yii\web\YiiAsset',
          'yii\bootstrap\BootstrapAsset',
      ];
  }
  </code></pre>
  
  <p>But all I get when loading the backend index is this:</p>
  
  <pre><code>http://localhost:8888/backend/web/css/custom.cssFailed to load resource: the server responded with a status of 404 (Not Found)
  </code></pre>
  
  <p>Sorry for the noob question and thanks in advanced. Just want to share a css between frontend and backend.</p>