Bug: Generics are not handled correctly in TypeScript definition output

[mattatz]

Thank you for updating Tsify project! 😃

I encountered an issue while using the tsify_next::Tsify derive macro.
When defining a struct with generics, the generated TypeScript definition does not handle the generics correctly.

Specifically, when I define:

#[derive(tsify_next::Tsify)]
pub struct Polyline<const D: usize> {
    pub points: Vec<Point<f64, D>>,
}

the index.d.ts file incorrectly outputs:

export interface Polyline {
    points: Point<number, D>[];
}

The generic D is not handled properly, which causes type definition issues in TypeScript.

[siefkenj]

Yes, it appears const generics should be handled differently!

If you're interested in attempting a PR for this feature, please let me know.