add license

crypto_kem/saber/clean/LICENSE

@@ -1 +1,8 @@
-TODO
+`Software implementation of Rainbow for NIST R2 submission' by Ming-Shing Chen
+
+To the extent possible under law, the person who associated CC0 with
+`Software implementation of Rainbow for NIST R2 submission' has waived all copyright and related or neighboring rights
+to `Software implementation of Rainbow for NIST R2 submission'.
+
+You should have received a copy of the CC0 legalcode along with this
+work.  If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.