R: Vignettes and other documentation

# Vignettes and other documentation

## Vignettes from package 'keras3'

keras3::custom_train_step_in_tensorflow |  | Customizing what happens in `fit()` with TensorFlow | HTML | source |
keras3::distributed_training_with_tensorflow |  | Multi-GPU distributed training with TensorFlow | HTML | source |
keras3::distribution |  | Distributed training with Keras 3 | HTML | source |
keras3::functional_api |  | The Functional API | HTML | source |
keras3::getting_started |  | Getting Started with Keras | HTML | source |
keras3::intro_to_keras_for_engineers |  | Introduction to Keras for engineers | HTML | source |
keras3::intro_to_keras_for_researchers |  | Introduction to Keras for Researchers | HTML | source |
keras3::making_new_layers_and_models_via_subclassing |  | Making new layers and models via subclassing | HTML | source |
keras3::sequential_model |  | The Sequential model | HTML | source |
keras3::serialization_and_saving |  | Save, serialize, and export models | HTML | source |
keras3::training_with_built_in_methods |  | Training & evaluation with the built-in methods | HTML | source |
keras3::transfer_learning |  | Transfer learning & fine-tuning | HTML | source |
keras3::understanding_masking_and_padding |  | Understanding masking & padding | HTML | source |
keras3::writing_a_custom_training_loop_in_tensorflow |  | Writing a training loop from scratch in TensorFlow | HTML | source |
keras3::writing_your_own_callbacks |  | Writing your own callbacks | HTML | source |