[question] Exposed members on Polka class

[43081j]

As part of some migrations, i've noticed myself needing the following members from Polka:

• Polka#handler - so i can bind it to request myself rather than calling listen
• wares - i want to create a new Polka which has the same middleware stack as another. for now i've literally set b.wares = a.wares but maybe we should have a method for this?
• onError - i want to set the error handler after instantiating Polka

basically, can i rely on these 3 things being part of the public interface? (i.e. you won't remove them without a new major)

and if not, what could we introduce to cover the same use cases in a supported way?