Method context is lost when placed inside objects

[barelyhuman]

This is a this problem.

When the polka instance is placed inside an object, it looses it's own this binding.

One of my repo's handles this by taking in the contructor and binding the used methods again, but I wanted to know
if it would be possible to add them in the source itself?

Here's the file doing it for a particular use case.
https://github.com/barelyhuman/preact-ssr-starter/blob/3cb40c7eaf4bcdf985eafdd87efd0fc68e0ce767/src/lib/polka.js

I'm not sure of how often people have this usecase considering it is a micro server, but if it makes sense I don't mind raising a PR