docs: fix contributing link in readme (#1723)

Author: raoulmillais

README.md

@@ -1014,7 +1014,7 @@ IPFS implementation in JavaScript is a work in progress. As such, there's a few
 
 ### Want to hack on IPFS?
 
-[![](https://cdn.rawgit.com/jbenet/contribute-ipfs-gif/master/img/contribute.gif)](https://github.com/ipfs/community/blob/master/contributing.md)
+[![](https://cdn.rawgit.com/jbenet/contribute-ipfs-gif/master/img/contribute.gif)](https://github.com/ipfs/community/blob/master/CONTRIBUTING.md)
 
 ## License