Unfortunately, it doesn't. That was actually the reason I built this originally - there's no easy way to control read/write access to a file on S3 without using some sort of external locking system.
It's not the intended purpose but they can be used like this. Lock files can be written, will fail if they already exist - that gets you a distributed equivalent to flock doesn't it?
They are valid solutions for this use-case; the main drawback is you need to set up and maintain a ZooKeeper cluster. Lockable is intended as a simpler and faster-to-use alternative.
AWS recommends using dynamo and has a Java reference implementation. Afaik GCP doesn't support locks either. Azure supports locks on blob store (their object store service)