fix: typescript return type annotations (#97)

* Fix return types for createRequestError, formatGraphQLErrors

* Add build to prepare

* Revert "Add build to prepare"

This reverts commit 2905f8d.

* Remove 'default' keyword.

Co-authored-by: David Emanuel Luksic <david.luksic@ablacon.com>

src/index.d.ts

@@ -303,5 +303,16 @@ export type GraphQLResponseErrors = Array<{
   stack?: string[];
 }>;
 
-export function createRequestError(request: RelayRequestAny, response?: RelayResponse);
-export function formatGraphQLErrors(request: RelayRequest, errors: GraphQLResponseErrors);
+export class RRNLError extends Error {
+  constructor(msg: string);
+}
+
+export class RRNLRequestError extends RRNLError {
+  req: RelayRequestAny;
+  res?: RelayResponse;
+
+  constructor(msg: string);
+}
+
+export function createRequestError(request: RelayRequestAny, response?: RelayResponse): RRNLRequestError;
+export function formatGraphQLErrors(request: RelayRequest, errors: GraphQLResponseErrors): string;