Add font-display default

[abea]

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

I'm suggesting we include font-display: fallback; on html or similarly. Just learned about it, but if supported (most do) it'll allow a short period of invisible text (~100ms) as fonts load, then if it's taking longer the browser will show a fallback font from the font-family. This would be meant to improve content access just in case the web font is too large or the user's connection is bad.

[bgantick]

I'm all for this. Please PR.