Add prettify-ts-plugin

[LukeAbby]

This is rather rudimentary at the moment. Here's things that need to be explored further before it stops being a draft:

• Actual reimplementation of prettification rather than a mostly faithful reproduction of what tsserver is doing.
• An actual monorepo setup. As it's currently set up, it's basically two separate packages.

[mylesmmurphy]

Hey @LukeAbby - this draft looks great so far. I've been learning about TS LSP's a bit over the past week and attempted to add the prettification myself as well, but ran into the same issue you mentioned where it gets complicated. However, I agree that ts-morph is probably doing too much. I'm really excited to see where you go with this, I absolutely believe this is the future of this project 🥳