Added customization of manifest using svelte.config.js

[SergeantWeb]

Simple feature added :

You can now customize manifest using svelte.config.json

Usage example

Customize the manifest to name our extension Test extension

// your-project/sveltekit.config.js
import adapter from 'sveltekit-adapter-browser-extension'

/** @type {import('@sveltejs/kit').Config} */
const config = {
	kit: {
		adapter: adapter({
			manifest: {
				name: "Test extension" // Customize app name in manifest
			},
		}),
		appDir: 'ext',
		prerender: {
			default: true
		}
	}
};

export default config;

[antony]

I like the idea of this. I might need to create a new PR as the project now supports multiple manifest versions since this PR was made.