Introduce JSON Schema–based converter generator

[akoenig]

This PR introduces a JSON Schema–based generator capable of creating new converter functions for Genie.

The generator can be controlled via the configuration file genie.config.json:

{
  "converters": [
    {
      "id": "package-json",
      "name": "Support for package.json",
      "source": {
        "type": "json-schema",
        "url": "https://json.schemastore.org/package.json"
      },
      "output": {
        "format": "json"
      }
    }
  ]
}

It is possible to add new converters by specifying a JSON Schema URL in this config file. Once a converter is defined here, running ⁠pnpm build will generate it and compile Genie as usual.

After building, the converter can be imported as usual:

import { packageJSON } from '@overengineering/genie'

export default packageJSON({
  // ...
})

Closes #4.

[schickling]

• genie.config.json -> src/generate-plugins.ts
  • bring back support for business logic (e.g. validation)
  • override stringify