Most of types just derive it using proc_macro directly. Some of value
types need manual impl.
In my current plan, this new trait will be used in bug 1434130 to expose
values as well.
Bug: 1455576
Reviewed-by: emilio
MozReview-Commit-ID: LI7fy45VkRw
This will allow #19659 to use derive on display using:
#[parse(aliases = "-webkit-flex")]
Flex,
#[parse(aliases = "-webkit-inline-flex")]
InlineFlex,
And such.