Fix contribution link, remove {{package}}

Author: jsarmientoOB

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 Contributions are **welcome** and will be fully **credited**.
 
-We accept contributions via Pull Requests on [Github](https://github.com/yajra/{{package}}).
+We accept contributions via Pull Requests on [Github](https://github.com/yajra/laravel-datatables-buttons).
 
 
 ## Pull Requests