[cli] if no instant module found in package.json, prompt to install one

[stopachka]

Context
When we generate files for the user, we need some instant module to exist. This is because in schema.ts for example, we need to generate an import statement like:

import { i } from '@instantdb/react'

Previously:

1. We only detected instantdb/react or instantdb/core.
2. We would fail if they weren't there

This PR makes the CLI more helpful, by:

1. Detecting react, core, react-native, and admin
2. If none are detected, prodding the user to choose one and installing it for them.

When a module is detected:

If no module is detected:

@dwwoelfel @nezaj

[github-actions]

View Vercel preview at instant-www-js-getorinstall-jsv.vercel.app.

[dwwoelfel]

Delightful!