v2 RC1 Changes (#7)

- Changes `items` and `hasItems` on `DocumentList` to be properties
- Updates dependent option/result library, which contains similar changes

Reviewed-on: #7

tests/unit/Mapper/CountMapperTest.php

@@ -21,6 +21,6 @@ class CountMapperTest extends TestCase
     #[TestDox('map() succeeds')]
     public function testMapSucceeds(): void
     {
-        $this->assertEquals(5, (new CountMapper())->map([5, 8, 10]), 'Count not correct');
+        $this->assertEquals(5, new CountMapper()->map([5, 8, 10]), 'Count not correct');
     }
 }