`&self` and `&Ruby`

[ankane]

Hi, I have a small API suggestion for using &self with &Ruby to make things more consistent.

Methods without &Ruby can use:

pub fn hello(&self, ...)

but methods with &Ruby need to use:

pub fn hello(ruby: &Ruby, self_: &Self, ...)

(and use self_ instead of self in the method body)

It'd be nice if there was support for:

pub fn hello(&self, ruby: &Ruby, ...)

like PyO3:

pub fn hello(&self, py: Python<'_>, ...)