Add font-display to generated @font-face

Feature Requests Website Builder Request
1

Per now, a generated block for the font-face looks like:

@font-face {
  font-family: 'Montserrat';
  font-style: italic;
  font-weight: 400;
  src: url(/g/static/s/montserrat/v29/JTUQjIg1_i6t8kCHKm459WxRxy7mw9c.woff2) format('woff2');
  unicode-range: ...;
}

It would be nice to be able to configure (or at least set a default) for the font-display so we can set something like:

font-display: swap;

This would improve pagespeed tests. Ref: Ensure text remains visible during webfont load  |  Lighthouse  |  Chrome for Developers