* Add support for #[wasm_bindgen(inspectable)]
This annotation generates a `toJSON` and `toString` implementation for
generated JavaScript classes which display all readable properties
available via the class or its getters
This is useful because wasm-bindgen classes currently serialize to
display one value named `ptr`, which does not model the properties of
the struct in Rust
This annotation addresses rustwasm/wasm-bindgen#1857
* Support console.log for inspectable attr in Nodejs
`#[wasm_bindgen(inspectable)]` now generates an implementation of
`[util.inspect.custom]` for the Node.js target only. This implementation
causes `console.log` and friends to yield the same class-style output,
but with all readable fields of the Rust struct displayed
* Reduce duplication in generated methods
Generated `toString` and `[util.inspect.custom]` methods now call
`toJSON` to reduce duplication
* Store module name in variable
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