make Jsf generic on data

[AlexErrant]

Before this change, dataChangeCallback's type parameter is unknown:

After this change, if you construct Jsf manually, you get the correct type:

This (unfortunately) only works for manual construction because it is impossible (AFAIK) for HTMLElementTagNameMap to have a generic that can infer its usage like as below:

declare global {
	interface HTMLElementTagNameMap {
		'json-schema-form': Jsf<T>;
	}
}

However, manual construction is fine for frameworks like Solid (tested in my project - IDK about others).

---

As an aside, I see #14 and wouldn't mind trying to take a crack at fixing some of the TS and/or CICD issues.

[JulianCataldo]

Hello. Thanks for the suggestion. I'm planning to rehaul quite a few things on this project, but can't make promises right now at when.
I'll definitely add more flexibility and include your changes as this is something lacking now (more type safety on the public API side).

Thanks!