MC-16046: Leverage the font-display CSS feature to ensure text is user-visible while webfonts are loading

- Add font display swap from icons;

Author: adifucan

app/design/frontend/Magento/blank/web/css/source/_icons.less

@@ -8,6 +8,7 @@
         @family-name: @icons__font-name,
         @font-path: @icons__font-path,
         @font-weight: normal,
-        @font-style: normal
+        @font-style: normal,
+        @font-display: swap
     );
 }