Please add a license

[petronny]

Hi, thank you for bring us this awesome tool.

I create a fork of your code and uploaded my changes at https://github.com/petronny/pinyin-completion.

However, I recently find modifying any of your code is not allowed unless there is a license file. So technically we can't even create pull requests to contribute to this project.

Please consider add a license like MIT or GPLv3 to allow us contribute to this project.

[Freed-Wu]

Github Contribution activity display the author has left from 2016. I am afraid that he cannot accept any message from github. I plan to rewrite https://github.com/petronny/pinyin-completion/tree/dev to avoid this problem.