extensions/npm/src/preferred-pm.ts/isYarnPreferred
async function isYarnPreferred(pkgPath: string) {
	if (await pathExists(path.join(pkgPath, 'yarn.lock'))) {
		return true;
	}

	try {
		if (typeof findWorkspaceRoot(pkgPath) === 'string') {
			return true;
		}
	} catch (err) { }

	return false;
}