Update The Pint Book to focus on `pint` as main CLI

[mitchmindtree]

This totally slipped my mind while finishing up #659, but I'm realising I should have also updated the book for this?

Perhaps we can still mention pintc and that it's available as a more minimal tool, but that most package creation, building and management should happen via pint?

We'll probably also want:

• A manifest reference, covering all fields in the manifest.
• A command reference (generated via pint --help?

cc @mohammadfawaz might have some thoughts on how this should be structured?

[mohammadfawaz]

Yeah I agree with the above. The focus should be on the pint tool instead of the pintc CLI tool. We would have a tooling section that covers pint at the end of the book. I think it's fine to hardcode the features for now but we can decide to automate doc generation in the future.