Add SixtyFPS

[LeoniePhiline]

Freshly announced and promising (IMHO):

• https://github.com/sixtyfpsui/sixtyfps
• https://sixtyfps.io/releases/0.1.1/docs/rust/sixtyfps/
• https://sixtyfps.io/blog/announcing-sixtyfps-0.1.html

[Max]

But it already added. Anyway i'd recommend to remove CSS tag, beacause there is no CSS.

[Jay]

Has now been added, thank you! Closing. Next PR will remove CSS tag.