Support for lock extensions

[hexcowboy]

Implementation for https://redis.io/docs/reference/patterns/distributed-locks/#making-the-algorithm-more-reliable-extending-the-lock

See: Node implementation

Let me know if you'd accept a PR for this, I can create one.

Update: I have already created this in a repository I maintain for redlock, so I will not be opening a PR but will leave this open for anyone who may want to contribute to this repository

[aig787]

@hexcowboy I'd definitely be open to a PR for this. Thanks!