feat(type-safe-api): support documentation generation for websocket apis

[cogwirrel]

Convert the OpenAPI spec to AsyncAPI, and use AsyncAPI's documentation generators for html and markdown documentation.

Note that there's a race condition when running two asyncapi generate commands at the same time - not sure exactly what the conflict is, have tried a few things like copying node_modules from ~/.pdk dir instead of symlinking, but the issue persists. As a workaround, we force the asyncapi documentation builds to run sequentially to ensure they do not conflict.

Fixes #742