add optional param for Schema.arr to specify objects in array (#159)

Co-authored-by: David Motsonashvili <[email protected]>

generativeai/src/main/java/com/google/ai/client/generativeai/type/FunctionDeclarations.kt

@@ -232,12 +232,17 @@ class Schema<T>(
         nullable = false,
       )
 
-    /** Registers a schema for an array */
-    fun arr(name: String, description: String) =
+    /**
+     * Registers a schema for an array.
+     *
+     * @param items can be used to specify the type of the array
+     */
+    fun arr(name: String, description: String, items: Schema<out Any>? = null) =
       Schema<List<String>>(
         name = name,
         description = description,
         type = FunctionType.ARRAY,
+        items = items,
         nullable = false,
       )