title: Angular Material - Can't resolve '@angular/material/theming'
body: <p>I have followed the <a href="https://material.angular.io/guide/theming" rel="noreferrer">official guide</a> and created a <code>app-theme.scss</code> with the following content:</p>
  
  <pre><code>@import '~@angular/material/theming';    
  @include mat-core();    
  $candy-app-primary: mat-palette($mat-indigo);
  $candy-app-accent:  mat-palette($mat-pink, A200, A100, A400);    
  $candy-app-warn:    mat-palette($mat-red);    
  $candy-app-theme: mat-light-theme($candy-app-primary, $candy-app-accent, $candy-app-warn);    
  @include angular-material-theme($candy-app-theme);
  </code></pre>
  
  <p>Content of <code>styles.css</code>:</p>
  
  <pre><code>@import './app-theme.scss';
  </code></pre>
  
  <p>However, I always get the following error during compilation: <code>Module not found: Error: Can't resolve '@angular/material/theming'</code>. What must I do to make it work?</p>