Create LICENSE

[luiz-brandao]

First of all, thank you for this great package!

I took the liberty add this license file based on the MIT license specified in the composer file.

For more details about adding a license: https://help.github.com/en/github/creating-cloning-and-archiving-repositories/licensing-a-repository https://help.github.com/en/github/building-a-strong-community/adding-a-license-to-a-repository