Declare @doc and @resolver directive

These declarations remove a lot of warnings from the PHPStorm
GraphQl plugin while editing schema.graphqls files.

Author: Vinai

app/code/Magento/GraphQl/etc/schema.graphqls

@@ -1,6 +1,42 @@
 # Copyright © Magento, Inc. All rights reserved.
 # See COPYING.txt for license details.
 
+directive @doc(description: String="") on QUERY
+    | MUTATION
+    | FIELD
+    | FRAGMENT_DEFINITION
+    | FRAGMENT_SPREAD
+    | INLINE_FRAGMENT
+    | SCHEMA
+    | SCALAR
+    | OBJECT
+    | FIELD_DEFINITION
+    | ARGUMENT_DEFINITION
+    | INTERFACE
+    | UNION
+    | ENUM
+    | ENUM_VALUE
+    | INPUT_OBJECT
+    | INPUT_FIELD_DEFINITION
+
+directive @resolver(class: String="") on QUERY
+    | MUTATION
+    | FIELD
+    | FRAGMENT_DEFINITION
+    | FRAGMENT_SPREAD
+    | INLINE_FRAGMENT
+    | SCHEMA
+    | SCALAR
+    | OBJECT
+    | FIELD_DEFINITION
+    | ARGUMENT_DEFINITION
+    | INTERFACE
+    | UNION
+    | ENUM
+    | ENUM_VALUE
+    | INPUT_OBJECT
+    | INPUT_FIELD_DEFINITION
+
 type Query {
 }