Documentation on how to use `geoarrow-wasm` from a standalone rust crate

[kylebarron]

I.e. it should be possible for me to publish geoarrow-wasm to crates.io and give an example of using that with a custom operation.

pub use geoarrow_wasm::*;

• Use no-default-features on the geoarrow_wasm dependency... only bring in the core geoarrow data structures and bindings, without geo algorithms.
• Example of some custom operation on the data arrays

[kylebarron]

Maybe it would be best to mimic the geoarrow crate layout?