feat(css): Update syntax for <generic-family>

[skyclouds2001]

Description

the <generic-family> is used by font-family, update it to match the latest spec and browser implement:

split <generic-family> into <generic-complete> and <generic-incomplete>, add support for non-standatd emoji and fangsong value

also remove the <generic-name> type which is never used

Motivation

https://drafts.csswg.org/css-fonts/#propdef-font-family

Additional details

Related issues and pull requests

[otomad]

Actually I still don't know how to use <generic-script-specific> and generic() function in font-family, it doesn't seem to work.

e.g. generic(fangsong) generic(kai) generic(khmer-mul) generic(nastaliq).

[skyclouds2001]

Actually I still don't know how to use <generic-script-specific> and generic() function in font-family, it doesn't seem to work.

e.g. generic(fangsong) generic(kai) generic(khmer-mul) generic(nastaliq).

These are not added because they are not supported by any platform at present

[dipikabh]

Looks good, thank you!