feat: add cli command "init"

[bonustrack]

Add a command init in Checkpoint cli to initiate a project with a setup like checkpoint-template repository (probably by doing a git clone of the repo), this will be much easier for anyone to get started.

[bonustrack]

Ok sure, feel free to make a PR for this, this is inspired by TheGraph SDK init command, learn more here: https://thegraph.com/docs/en/subgraphs/quick-start/#3-initialize-your-subgraph.