fix(serverless): change response handler type to accept promises (#599)

Author: Gabrola

.changeset/rare-apes-play.md

@@ -0,0 +1,5 @@
+---
+'@ts-rest/serverless': patch
+---
+
+Change response handler type to accept promises

libs/ts-rest/serverless/src/lib/types.ts

@@ -132,7 +132,7 @@ export type ServerlessHandlerOptions<
       response: TsRestResponse,
       request: TsRestRequest & TRequestExtension,
       args: TPlatformArgs,
-    ) => TsRestResponse | void
+    ) => TsRestResponse | Promise<TsRestResponse> | void | Promise<void>
   >;
 };