title: Set gradient color on Angular mat-icon
body: <p>How can I set gradient color on mat-icon Angular? I can set the color in css e.g., red, green, or any other solid colors like
  <code>mat-icon {  color: red;  }</code>. But when trying to set to a gradient color like
  <code>mat-icon {linear-gradient(to right, xxxxxx, #xxxxxx);}</code>
  it has no effect. Thanks:)</p>