[style] Automatically generate value enumerations and parser

[usadson]

Currently, the parsing of CSS in the engine by retina-style-parser translates the CSS syntax into the format in retina-style, but doing this by hand is quite tedious and error-prone. It would be better to have the properties in some kind of syntax file that will generate a Rust file at compile time.

Looks like W3C already has a JSON representation for the CSS properties, see https://github.com/w3c/webref/tree/main/ed/css