Export NavigationDuplicated class

[LEW21]

What problem does this feature solve?

I want to do:

try {
	await router.push(...)
} catch (e) {
	if (e instanceof NavigationDuplicated) {}
	else {throw e}
}

Unfortunately I can't, because NavigationDuplicated is not exported.

What does the proposed API look like?

export NavigationDuplicated

[FranckFreiburger]

Please export this, it is quite annoying to compare to the error name.

[jonatahr]

@LEW21 and @FranckFreiburger, take a look:
#3047

You will be able to check the error type by property _type. This information must be documented.

[posva]

I'm closing this in favour of #3047

It's not final API as we want to align it with vue-router-next as much as possible to reduce breaking changes. It will probably be available through an additional property on the error instance to support every browser