fix: add imports

Author: saihaj

src/type/schema.d.ts

@@ -2,7 +2,7 @@
 /* eslint-disable import/no-cycle */
 
 import { Maybe } from '../jsutils/Maybe';
-import { ObjMap } from '../jsutils/ObjMap';
+import { ObjMap, ReadOnlyObjMap, ReadOnlyObjMapLike } from '../jsutils/ObjMap';
 
 import { SchemaDefinitionNode, SchemaExtensionNode } from '../language/ast';