feat: expose some types

[himself65]

I'm trying to implement some end-to-end encryption updates, like encryptUpdate(update, private) -> update, that allows the server to merge updates and decode updates...(just like obfuscateUpdate), but the difference is contents are encrypted by privateKey. So that it can be safely saved to the server, but the update is still valid so that the server can validate if the document schema is correct.

Then, I found that some internal classes are not exposed, so it will make things hard to extend the existing logic. I would appreciate it if some internal types could be exposed to the downstream so that we can make the ecosystem better.

_{Huly®: YJS-445}

[himself65]

@dmonad any idea of this PR?

[dmonad]

Sure, gonna make a release soon!