Convert to monorepo

[jorins]

Due to the complexity of maintaining multiple versions of documentation (#6), we have the need for developing tooling that would be best kept outside the main project. This is not unlikely to happen in other ways too, and working proactively with setting up a monorepo is probably a good idea.

Another potential use case already is setting up separate modules for node and web that the main module can re-export, but they can be tested individually under different circumstances with regards to available types and APIs.

A change to a monorepo structure would probably mean switching to pnpm, which should not cause any problems by itself. We shouldn't need tools like turbobuild from day one but I could be wrong.