LICENSE: propose MIT license

[phillco]

The existing code doesn't have an explicit license. It's probably good to set one to avoid ambiguity.

I've used the same MIT license that knausj uses here, but let me know if a different one would be preferred:

https://github.com/knausj85/knausj_talon/blob/master/LICENSE

[phillco]

cc past contributors @anonfunc @hbk619