[css-typed-om] CSSStyleValue normalization

[annevk]

If a property’s grammar is more complex than one of the types listed here, it normalizes to a raw CSSStyleValue

Normalizes above links to https://drafts.css-houdini.org/css-typed-om/#cssmath-normalize-a-math-expression which doesn't really make this sentence any clearer.

[tabatkins]

I switched the term for "turn a CSS value into a CSSStyleValue object" to "reify", so it is (a) more correct and (b) won't overlap with some of my "normalization" terms, so this is fixed now.