See: https://fontawesome.com/how-to-use/on-the-web/advanced/css-pseudo-elements
font-family: "Font Awesome 5 Free"; // Solid 900
font-family: "Font Awesome 5 Pro"; // Solid/Regular/Light 900/400/300
font-family: "Font Awesome 5 Duotone"; // Duotone 900
font-family: "Font Awesome 5 Brands"; // Brands 400
.icon::before {
display: inline-block;
font-style: normal;
font-variant: normal;
text-rendering: auto;
-webkit-font-smoothing: antialiased;
content: "insert-fa-icon-code";
font-weight: "insert-font-weight";
font-family: "insert-font-family";
}