Update README.md

Author: paulofaria

README.md

@@ -14,7 +14,7 @@ Looking for help? Find resources [from the community](http://graphql.org/communi
 
 This repo only contains the core GraphQL implementation. For a better experience when creating your GraphQL schema use [Graphiti](https://github.com/GraphQLSwift/Graphiti).
 
-## Contributions
+## Contributing
 
 Most of this repo mirrors the structure of the canonical GraphQL implementation written in Javascript/Typescript. If there is any feature missing, looking at the original code and "translating" it to Swift works, most of the time. For example: