Implement Error for ResourceTableError

[kayhhh]

When building for web, ResourceTable becomes annoying to use because the error type is not compatible with anyhow:

the trait `StdError` is not implemented for `ResourceTableError`, which is required by `Result<(), anyhow::Error>: FromResidual<Result<Infallible, ResourceTableError>>

So for example when implementing host functions, you must map_err every table error:

fn remove_node(&mut self, value: Resource<Node>) -> wasm_bridge::Result<()> {
    let rep = value.rep();
    self.table.delete(value).map_err(|e| anyhow!("{:?}", e))?;
}

When building for native, that line would simply be:

self.table.delete(value)?;

I would be happy to make a PR if you want as this shouldn't be difficult, just wasn't sure how you would want to go about it (for example using the thiserror crate).