* add testing for wasm

utilize wasm-bindgen-test as a developer dependency in order to
actively run wasm tests. wasm currently doesn't have support for
running doctests (and reportedly won't "anytime soon"), and in
order to actually run the tests we need a wasm environment.

the easiest of these to setup & use is wasm-pack which is primarly
built for nodejs. however, if it works in nodejs it should ideally
work in other wasm environments that are similar.

as such a wasm-pack (which utilizies wasm-bindgen) as a developer
dependency has been added that creates a simple error message,
and validates it contains the text of the error (and sections)
sans any formatting. this is meant to validate a base level
of functionality as time goes on.

* fix format

* only add dev-dependency for wasm32

* fix clippy warning

Co-authored-by: Jane Lusby <jlusby@yaah.dev>