Impl WasmType for FuncRef and ExternRef (#642)

impl WasmType for FuncRef and ExternRef

This allows to use FuncRef and ExternRef types with the TypedFunc API and everything that connects to it.

This functionality was trivial to add and simply forgotten in the reference-types implementation PR.

crates/wasmi/src/func/into_func.rs

@@ -6,6 +6,8 @@ use crate::{
     core::{Trap, ValueType, F32, F64},
     foreach_tuple::for_each_tuple,
     Caller,
+    ExternRef,
+    FuncRef,
     FuncType,
 };
 use core::{array, iter::FusedIterator};
@@ -179,6 +181,8 @@ impl_wasm_type! {
     type i64 = I64;
     type F32 = F32;
     type F64 = F64;
+    type FuncRef = FuncRef;
+    type ExternRef = ExternRef;
 }
 
 /// A list of [`WasmType`] types.