Implement this for non-STD ref counts

[Eh2406]

There are many libraries that have alternative implementations of ref counted pointers, we should probably check which of them can implement the trade defined in this crate.

[cark]

I never worked in a no_std context, it'll also take a little while for me to investigate this

[Eh2406]

To be clear I did not mean no_std, I meant ref counts that are implemented in crates instead of an STD. From a quick search:

• https://lib.rs/crates/servo_arc
• https://lib.rs/crates/rc-box
• https://lib.rs/crates/triomphe
• https://lib.rs/crates/refpool
• but there are more.

[cark]

still, might need to do it for no_std, I see there is a core::alloc::Rc type.

The triomphe crate doesn't allow for weak pointers, looks like we might have to introduce features 😢