fix: add docstring for image_size in Convnextv2 config (#33734)

add docstring for image_size

src/transformers/models/convnextv2/configuration_convnextv2.py

@@ -52,6 +52,8 @@ class ConvNextV2Config(BackboneConfigMixin, PretrainedConfig):
             The epsilon used by the layer normalization layers.
         drop_path_rate (`float`, *optional*, defaults to 0.0):
             The drop rate for stochastic depth.
+        image_size (`int`, *optional*, defaults to 224):
+            The size (resolution) of each image.
         out_features (`List[str]`, *optional*):
             If used as backbone, list of features to output. Can be any of `"stem"`, `"stage1"`, `"stage2"`, etc.
             (depending on how many stages the model has). If unset and `out_indices` is set, will default to the