Apply a license

[FlorentPoinsaut]

Hello,

Thank you for this great App! Please, could you apply a free/libre and open-source software licence to your code? I suggest you add the LICENSE GPLv3 (https://www.gnu.org/licenses/quick-guide-gplv3.html)?

Help by GitHub : https://help.github.com/en/articles/adding-a-license-to-a-repository

Thank you in advance.

Regards,