Add some README

[mjack3k]

Not gonna lie, a tiny bit of help on how to use it would have been helpful.

I somehow managed to figure it out thanks to some other issue that mentioned the usage and (at least according to the usrlock cli output) managed to unlock the phone. But some basic info would be greatly appreciated, what to install, what to do.

Might try doing one myself, but I'm afraid I might skip some important steps/information.