fix: make kind public
Otherwise one could not proxy `Handler::execute()` with the Handler own
type.
@@ -15,7 +15,7 @@ pub use stub::*;
use crate::guest::alloc::{Allocator, Collect, Commit};
use crate::Result;
-pub(crate) mod kind {
+pub mod kind {
use super::alloc;
use core::marker::PhantomData;
