Allow package.json customisation when using svelte-package

[tkvw]

Describe the problem

I'm always frustrated when svelte-package creates a package.json not to my liking.
In a monorepo I have specified the following two entries in the original package.json to allow a component library to work with the svelte-kit generated website:

  "svelte": "src/lib/index.ts",
  "types": "src/lib/index.ts",

This is shamefully copied by the svelte-package library.

Describe the proposed solution

Allow packageJson generation to be overwritten in the package config section of svelte.config.js.

/** @type {import('@sveltejs/kit').Config} */
const config = {
  preprocess: preprocess(),
  kit: {
    adapter: adapter()	
  },
  package: {
	mergePackageJson: (original,proposed) => proposed // default = proposed, false = skip 
  }
};

Alternatives considered

Post edit the generated package.json

Importance

would make my life easier

Additional Information

No response

[dummdidumm]

Somewhat related to #6824

[tkvw]

FWIW I create a svelte-package-unpack gist which will copy the package content to the root folder and creates appropriate package.json files in subfolders. This allows typescript to find the correct typings and use the package in place (for use in a monorepo).

Make sure to add the generated folders to the .gitignore
The gist can simply be run by npx after build:

// package.json
"scripts": {
   "build": "svelte-kit sync && svelte-package && npx --yes https://gist.github.com/tkvw/ade8c42068fab1610bcad241649fd745/dfb552d06cea7ae9821456d9ac0678bc428f1e9b",
}

I think having the transpiled javascript in the root package with an appropriate .gitignore is best solution.