CONTRIBUTING.md in extzstd-0.2

- old
+ new

@@ -37,6 +37,6 @@
 ## Coding Style  
 * 4 spaces for indentation rather than tabs
 
 ## License
 By contributing to Zstandard, you agree that your contributions will be licensed
-under the [LICENSE](LICENSE) file in the root directory of this source tree.
+under both the [LICENSE](LICENSE) file and the [COPYING](COPYING) file in the root directory of this source tree.