refactor(interface): Use default export for implementation

[ExE-Boss]

⚠️ WARNING: BREAKING CHANGE

Fixes #59

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This changes the implementation class syntax to allow CommonJS and ES2015 style default exports:

// CommonJS
/** @type {WeakMap<Foo, PrivateData>} */
const fooPrivateData = new WeakMap();

class Foo {
	// implementation
}
module.exports = exports = Foo;

export.init = function(instance, privateData) {
	fooPrivateData.set(instance, privateData);
}

// ES2015
/** @type {WeakMap<Foo, PrivateData>} */
const fooPrivateData = new WeakMap();

export default class Foo {
	// implementation
}

export function init(instance, privateData) {
	fooPrivateData.set(instance, privateData);
}

---

TODO:

• Add tests for the importStar(…) helper.
• Update documentation

[domenic]

This is not true; jsdom only operates on CommonJS modules.

[ExE-Boss]

Well, you do need to transpile ES2015 modules to be able to use them in Node.

[domenic]

Yes. That is not a supported scenario, so please remove it.

[domenic]

I am not interested in this addition. Please remove it.

[ExE-Boss]

Which? The JSDoc or the entire utils.importStar(…) function?

[domenic]

The importStar function itself.