Add LICENSE

LICENSE

+This work is licensed under [CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/).
+
+This license requires that reusers give credit to the creator. 
+It allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, for noncommercial purposes only. 
+If others modify or adapt the material, they must license the modified material under identical terms.