extensions/npm/src/preferred-pm.ts/isPNPMPreferred
async function isPNPMPreferred(pkgPath: string): Promise<PreferredProperties> {
	if (await pathExists(path.join(pkgPath, 'pnpm-lock.yaml'))) {
		return { isPreferred: true, hasLockfile: true };
	}
	if (await pathExists(path.join(pkgPath, 'shrinkwrap.yaml'))) {
		return { isPreferred: true, hasLockfile: true };
	}
	if (await findUp('pnpm-lock.yaml', { cwd: pkgPath })) {
		return { isPreferred: true, hasLockfile: true };
	}

	return { isPreferred: false, hasLockfile: false };
}