Add a way to extend/modify props & options of an existent component

[kizu]

Similar to .extend and .withComponent for styled-components, but in a way it would be possible to redefine just everything, returning a new component based on original params merged with the new ones.

[kizu]

Desired API:

const NewButton = bemto(Button, {/* overrides */});

If the Button would provide some way for bemto() to know how it was created, we can re-use what was there instead of wrapping it in a new component.