Fix $subscribe and $subscribeAction return types

Author: luxaritas

src/interfaces.ts

@@ -96,9 +96,9 @@ export interface ProxyWatchers {
   $subscribe (
     mutationfield :string,
     callback :( payload :any ) => void,
-  ) :void
+  ) :() => void
 
-  $subscribeAction ( actionField :string, callbackOrObj :SubScribeActionCallback | SubScribeActionObject ) :void
+  $subscribeAction ( actionField :string, callbackOrObj :SubScribeActionCallback | SubScribeActionObject ) :() => void
 
 }
 
@@ -107,4 +107,4 @@ type SubScribeActionCallback = ( payload :any ) => void;
 type SubScribeActionObject = {
   before: ( payload :any ) => void;
   after: ( payload :any ) => void;
-}
+}