fix: export non-Procedures TypeScript types

[espeon]

Should close #320.

Typemaps should now be correctly merged and exported. Let me know of any issues or things I've overlooked.

[yuezk]

This PR fixes the issue. But it couldn't handle the generic type. For example, the following code:

#[derive(Debug, Serialize, Type)]
pub(crate) struct Success<T: Serialize + Type = ()> {
  data: T,
}

...will produce:

export type Success = { data: T };

But previously with the older versions crates:

specta = "=2.0.0-rc.1"
specta-macros = "=2.0.0-rc.1"
rspc = { version = "1.0.0-rc.5", features = ["tauri"] }

It can produce the correct types.

export type Success<T> = { data: T }

[oscartbeaumont]

Happy to merge once the comments are addressed. I do agree with @yuezk's comment.

Thanks for taking the time to do a PR and thanks @yuezk for the feedback!