Fix event.subscribe types: arc.events.subscribe does not return unkno…

…wn, but a function returning a promise or not, depending on whether an async or callback function was provided to subscribe

dont care about args to callbacks

types/events.d.ts

@@ -10,21 +10,14 @@ interface Params<Payload> {
  payload: Payload;
 }
 
-// Consumers of this library should not care exactly what this is. Just that
-// it's a lambda function which should be exported as a handler.
-type LambdaFunction = unknown;
-
 interface EventsOrQueues<PublishResult> {
  publish<Payload = any>(params: Params<Payload>): Promise<PublishResult>;
  publish<Payload = any>(
  params: Params<Payload>,
  callback: Callback<PublishResult>,
  ): void;
- subscribe<Event = any>(
- handler:
- | ((event: Event) => Promise<void>)
- | ((event: Event, callback: Callback<void>) => void),
- ): LambdaFunction;
+ subscribe<Event = any>(handler: (e: Event) => Promise<void>): (e: Event) => Promise<void>;
+ subscribe<Event = any>(handler: (e: Event, callback: Function) => void): (e: Event, context: any, callback: Function) => void;
 }
 
 export type ArcEvents = EventsOrQueues<SnsPublishResponse>;