[Feature Request] extended `import` utilising package manager to provide exportability

[TGTGamer]

Is your feature request related to a problem? Please describe.
Extension of the import utility to enable user to import from node_modules folders, enabling the ability to extend from external packages.

Describe the solution you'd like
A simple way to extend from node_modules folders. From the looks of it, an refactor of

zenstack/packages/schema/src/utils/ast-utils.ts

Lines 96 to 106 in b4579c7

	export function resolveImportUri(imp: ModelImport): URI | undefined {
	if (imp.path === undefined || imp.path.length === 0) {
	return undefined;
	}
	const dirUri = Utils.dirname(getDocument(imp).uri);
	let grammarPath = imp.path;
	if (!grammarPath.endsWith('.zmodel')) {
	grammarPath += '.zmodel';
	}
	return Utils.resolvePath(dirUri, grammarPath);
	}

I assume there would be an additional step somewhere within the language file, and probably within the vscode extension, however haven't yet discovered those locations (will update once I have)

Describe alternatives you've considered
Keeping all my files in a single project and making endless copies of them into each individual project. Meaning there's no single source of truth, making it easy for one scheme to fall out of sync with another....