doc update

        You can modify the postprocessing object (pp) to update the images in the batch, remove images, add images, etc.

        If the number of images is different from the batch size when returning,

        then the script has the responsibility to also update the following attributes in the processing object (p):

          - p.prompts

          - p.negative_prompts

          - p.seeds

          - p.subseeds

        then the script has the responsibility to also update the following attributes in the processing object (pp):

          - pp.prompts

          - pp.negative_prompts

          - pp.seeds

          - pp.subseeds

        **kwargs will have same items as process_batch, and also:

          - batch_number - index of current batch, from 0 to number of batches-1