Display for Errors, return error from WASM

[ThomasdenH]

This PR adds Display and Error impls for the errors, and returns a JsError with the formatted string to WASM. I have updated the documentation and demo to reflect this, and also fixed the warnings Clippy gave me.

[fpapado]

Neat, thank you @ThomasdenH!

I had a note to circle back for explicit errors on a branch, so this is very fitting! I really like thiserror
We might want to expose more information in the errors in the future, but I bet that can be in another PR.

I'll take a final look at this once I'm home in a few hours, and merge :)

(Aside: do you know, by any chance, if there was any resolution to rustwasm/wasm-bindgen#1017? It's what kept me from making the js_sys::Error conversion in the first place, but maybe that doesn't matter much.)

[ThomasdenH]

I'm not sure there is a resolution to the issue. There is some additional discussion here: rustwasm/wasm-bindgen#1742, which gives the recommendation to use a JsError instead of throwing a string.

[fpapado]

Sounds good! I tried the demos and so on and they seemed to work.
Thank you again for this PR. I'll merge it now and get a release out later today.

[ThomasdenH]

Great!