font-family value with white spaces isn't quoted

[Gedevan-Aleksizde]

When I specify a font family name with white spaces (e.g., YuMincho +36p Kana, one of the standard Japanese font in MacOS ), font-family value isn't quoted in the exported svg file. So It sometimes isn't properly recognized when browsed or converted by rsvg::rsvg_pdf

For example:

par(family = "YuMincho 36p Kana")
plot(0, xlab = "", ylab = "", axes = F, main = "游明朝 +36ポかな")
dev.copy(svglite::svglite, "font.svg")
dev.off()
rsvg::rsvg_pdf("font.svg", "font-rsvg.pdf")

In this case, rsvg::rsvg_pdf embeds "Hiragino Mincho ProN" insteadly.