Default CSS as a contract

Friendly reminder that --serif is still missing. It was previously defined as

--serif: "Iowan Old Style","Apple Garamond",Baskerville,"Palatino Linotype","Times New Roman","Droid Serif",Times,"Source Serif Pro",serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";

There’s also a prefetch error for the webfont in Chrome Already reported in small error in the console.