Add separate license file

[dvzrv]

Hi! I package this project for Arch Linux.
Since the files are covered by a BSD license (AFAIK), it would be very good if a license file could be added to the repository.
I am required to package a license file (as this is a license type that has unique text in it, unlike e.g. GPL etc.) and currently have to revert to some sed-hack to get the license string out of the .zsh file.

[dvzrv]

@sunaku or whoever is currently maintaining this project, can you please look into this? Thank you! :)

[kocv59]

@dvzrv maintainers aren't doing anything to this project. Can you create a new patch 1.1.0-3 that includes da5f067. Doesn't work after zsh 5.8.