This commit migrates all our examples to using `wasm-pack build` to
compile their code and run `wasm-bindgen`. This should make it a bit
easier to understand the examples as there's less to follow during the
build step.
Webpack projects are all using `@wasm-tool/wasm-pack-plugin` as well so
the build step is simple `npm run serve`. Other examples which retain
`build.sh` are just using `wasm-pack build` now
Some examples have been failing to load in some browsers, and this
ensures that whenever the promise to load Rust code fails we log any
errors happening instead of accidentally failing silently.
This helped debug a bit in #897
