Add license declaration

[kubark42]

This is a great repo, but it looks like there's no clear licensing statement. Would it be possible to add the license either as LICENSE.md or in the README.md? Obviously many would love to see this open-sourced, but even if it's closed it's important to have clarity.

P.S. Without a specific license the files in this project are copyrighted under the standard fully restrictive international license. They can still be used in internal projects, but they and their compiled binaries cannot be redistributed.