This replaces the 'ws' library with built-in websockets so that we can mock a server and successfully connect to it. A simple test verifies that Unit is handling a message request and response as we expect it to.
This allows require() and import to work for even better compatibility between CJS and ESM consumers.
I dislike that this kills our ability for top-level awaits in example.ts, but seeing as how my primary use case for this library is a commonjs module, I think this is a fair trade-off.
Also changed "messages" to not encapsulate its export under the name "messages" to remove some repetition in importing "messages" and still needing to do "messages." to get the methods out. Now it's simple to import each message by name or group them under something like "messages" as desired on a per-library-user basis.
Refs:
* https://www.kravchyk.com/typescript-npm-package-json-exports/
* https://arethetypeswrong.github.io/
* https://evertpot.com/universal-commonjs-esm-typescript-packages/
