Feature Request: no_std support

[TooManyLimits]

Feature request

It would be nice if the externref crate did not require the standard library. When using it as a dependency, it's impossible to define a custom #[panic_handler], for example.

Why?

WASM applications often try to minimize file size, and a common way of doing this is to make the crate #![no_std] to remove unnecessary code from the standard library (such as the built in panic handler, in some cases). Making the crate #![no_std] compatible would enable projects depending on it to have smaller compiled file sizes.