Merge pull request #56 from ruudk/typehint-compat

Make SyncPromiseAdapter compatible with webonyx master

Author: mcg-web

src/Promise/Adapter/Webonyx/GraphQL/SyncPromiseAdapter.php

@@ -17,12 +17,12 @@
 
 class SyncPromiseAdapter extends BaseSyncPromiseAdapter
 {
-    protected function beforeWait(Promise $promise)
+    protected function beforeWait(Promise $promise): void
     {
         DataLoader::await();
     }
 
-    protected function onWait(Promise $promise)
+    protected function onWait(Promise $promise): void
     {
         DataLoader::await();
     }