.font-sans missing sans-serif

[tlgreg]

So the defaultConfig .font-sans font stack doesn't have sans-serif as the last fallback.
Although be unlikely that every font is missing, but if so the font stack actually falls back to Times New Roman on Chrome and Firefox (and most likely others).

ps.: Actually the only windows default in the list is Segoe UI.

[reinink]

Yeah, good point @tlgreg. I'll add that.