Expose scrollToTarget and document subclasses

[taion]

No description provided.

[taion]

cc @satazor, @vasco-santos

[satazor]

@taion Looks good.

I would prefer the callback though, for two reasons:

• Easier to use
• Less surface for breaking changes

Anyway I understand and respect your decision.

[taion]

It is easier to use, but I think the surface area is a bit lower here, in the sense that we're just exposing overridable methods in a standard-ish way, such that can be extended for other applications, instead of adding a specific carveout for a single callback.

Thanks for your patience here. I'll release shortly.