File System
Kun.chmod
chmod(path: string, mode: number): Promise<void>
await Kun.chmod('/path/to/file', 0o666);
Kun.chown
chown(path: string, uid: number, gid: number): Promise<void>
await Kun.chown('/path/to/file', 1000, 1002);
Kun.copyFile
copyFile(from: string, to: string): Promise<void>
await Kun.copyFile('from.txt', 'to.txt');