Make friendly JS app

[clbarnes]

The wasm bindings have some ergonomics issues (e.g. flattened coordinates); the interface in https://github.com/clbarnes/nblast-rs/blob/master/nblast-js/examples/nblast-app/index.js should be promoted to part of the library. I think this will require webpack e.g. https://github.com/rustwasm/wasm-bindgen/tree/main/examples/weather_report