title: Change checkbox design from square to circle
body: <p>Thank you for your help in advance.
  I'm trying to change the mat-checkbox design from square to circle.
  but is a little bit hard to find a way.</p>
  
  <p>Can you help me??</p>
  
  <p>I can change only the background with the code below.</p>
  
  <pre><code>mat-checkbox { 
    border-radius: 100%;
    color: rgb(0,178,0);
    /deep/ .mat-checkbox-background {
      background-color: rgb(0,178,0);
    }
    /deep/ &amp;.mat-checkbox-focused {
      .mat-ink-ripple {
        background-color: rgba(0, 178, 0, .26);
      }
    }
  }
  </code></pre>