Add doc comment to SchemaOptions model

Author: FionaBronwen

packages/graphql/lib/schema.tsp

@@ -5,6 +5,7 @@ using TypeSpec.Reflection;
 namespace TypeSpec.GraphQL;
 
 namespace Schema {
+  /** Options for configuring a GraphQL schema. */
   model SchemaOptions {
     /**
      * The name of the GraphQL schema. Used in the output filename when emitting