Function wasmtime_component_linker_instance_add_func 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn wasmtime_component_linker_instance_add_func(
    linker_instance: &mut wasmtime_component_linker_instance_t<'_>,
    name: *const u8,
    name_len: usize,
    callback: wasmtime_component_func_callback_t,
    data: *mut c_void,
    finalizer: Option<extern "C" fn(*mut c_void)>,
) -> Option<Box<wasmtime_error_t>>