为 stdweb crate 提供推导宏

此 crate 当前定义了一个用于 stdweb 的推导宏，允许您在 stdweb 之外定义自定义引用类型。

例如

#[derive(Clone, Debug, PartialEq, Eq, ReferenceType)]
#[reference(instance_of = "Error")]
pub struct Error( Reference );

#[derive(Clone, Debug, PartialEq, Eq, ReferenceType)]
#[reference(instance_of = "TypeError")]
#[reference(subclass_of(Error))]
pub struct TypeError( Reference );

然后您可以这样做

// You can use `try_into` to cast a `Value` to your type.
let error: TypeError = js!( return new TypeError(); ).try_into().unwrap();

// You can also pass your type freely into the `js!` macro:
js!( console.log( @{error} ); );