fix(deps): Updates graphql-yoga dependency to 1.6.0. Otherwise the example does not work - the directive resolvers are not invoked.

Author: sflahave

examples/custom-directives/package.json

@@ -3,6 +3,6 @@
     "start": "node ."
   },
   "dependencies": {
-    "graphql-yoga": "1.2.0"
+    "graphql-yoga": "1.6.0"
   }
 }