bugfix: implement Countable::count to provide 0|positive-int as return type

Signed-off-by: Maximilian Bösing <[email protected]>

Author: boesing

src/ArrayInterface.php

@@ -55,4 +55,9 @@ public function allSatisfy(callable $callback): bool;
      * @psalm-param callable(TValue):bool $callback
      */
     public function exists(callable $callback): bool;
+
+    /**
+     * @return 0|positive-int
+     */
+    public function count(): int;
 }