init / generate / onboarding

[threepointone]

This issue tracks the implementation of init, and the general onboarding process.

• You can run wrangler init (or optionally wrangler init <name>, and it'll generate a wrangler.toml file where it's called with a name and compatibility_date.
• We are considering expanding the types of configuration we accept: as ideas, it could be a .ts file (so you can typecheck your configuration), a .json file or included in package.json, and so on. (TODO: an issue just for configuration)
• We are considering rethinking --generate and the overall onboarding process. We may build create-workers-app (inspired by create-react-app and other like it) to provide a better onboarding experience, but also so we can upgrade the experience without much configuration in the future.

[threepointone]

• For v2, we won't have any new types of config (ts, a field package.json, etc), probably in a minor release after that.
• wrangler init now can generate a package.json/tsconfig

This issue should probably focus on create-workers-app. We should decide whether it's tied to the v2 release, and what shape it should take.

[threepointone]

Marking this as closed, we can open a fresh issue for create-workers-app / onboarding in general