Per language type overrides

[oscartbeaumont]

Allow override the default type = on a per language basis.

struct Demo {
   #[specta(type = Any, ts(type = String))]
   a: String,
}

or, allow a raw string override:

struct Demo {
   #[specta(type = Any, ts(raw = "string"))]
   a: String,
}

[oscartbeaumont]

I am really on the fence about supporting this. For now it's going to stay unimplemented unless someone can provide a compelling usecase. It does provide an escape hatch for Specta bugs but also we just gotta not have bugs.