Create index for utils package

Note that I'm dumping `SchemaReference`, which is unused, and came over
from codemirror-graphql. As that's the only caller/user of the
functionality, the functionality may as well live over there.

packages/graphql-language-service-utils/src/index.js

@@ -0,0 +1,23 @@
+/**
+ *  Copyright (c) Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the license found in the
+ *  LICENSE file in the root directory of this source tree.
+ *
+ *  @flow
+ */
+
+export {
+  getASTNodeAtPosition,
+  pointToOffset,
+} from './getASTNodeAtPosition';
+
+export {
+  Position,
+  Range,
+  locToRange,
+  offsetToPosition,
+} from './Range';
+
+export {validateWithCustomRules} from './validateWithCustomRules';