Consider auto-generating ts types

[mattyg]

There are several libraries to automate generation of rust types. We should consider generating and publishing holochain exposed types as a standalone npm package, which can become a dep of this library.

• tsify
• ts-rs
• typeshare
• specta

Keeping this issue here since it is specific to serving the js client, even though it would have to happen in the holochain repo.