Add font-display property to css
Event if the `font-display` property is not compatible with all navigators yet, it could be interesting to add it to the css `@font-face` in order to optimize the loading process.  

`font-display: block;` is comonly in use for icon fonts. 

More here : https://developer.mozilla.org/en-US/docs/Web/CSS/@font-face/font-display