A more thorough getting started guide.

[nixon-voxell]

Currently, we have a simple quickstart guide at README, however, it may be too simple for people who are a little new to Rust or Bevy or Typst or Vello.

This getting started guide should help users start from scratch with only little knowledge on the basics of Rust. And should also link users to external documentations when needed (e.g. Typst's docs)