Define return types for key() and current() in CursorInterface

Author: alcaeus

src/MongoDB/CursorInterface.stub.php

@@ -9,12 +9,16 @@
 
 interface CursorInterface extends \Iterator
 {
+    public function current(): array|object|null {}
+
     public function getId(): CursorId|\MongoDB\BSON\Int64;
 
     public function getServer(): Server;
 
     public function isDead(): bool;
 
+    public function key(): ?int;
+
     public function setTypeMap(array $typemap): void;
 
     public function toArray(): array;