h3 directly relies on crossws for it's WS handling, but doesn't make the crossws types available to consumers of h3. This in turn makes it quite hard to properly type functions that rely on the returned values in the WS handlers, as it forces the consumer of h3 to also add crossws as a devDependency and ensure that the version of crossws exactly matches the version in use by h3 to ensure there's no type conflicts. This is a pretty poor DX. By re-exporting the types used for the crossws logic that's relied on by h3 this problem is resolved.

I've identified Hooks, Peer, AdapterInternal, and Message as the ones you immediately run into when using defineWebSocketHandler, but there might be others. I didn't want to go as far as to export * as that'll add a bunch of unused types and other noise to h3s global scope as well.

Fixes #716