Add Upload Guide (keras-team#1847)

* Upload guide.

* KerasNLP upload guide.

* Address reviews.

* Add classifier example.

* Kaggle Hub --> Kaggle Models.

* Add model loading.

* Replace the toy dataset with IMDB dataset.

* Adress reviews.

* Some final fixes to make autogen run successful.

* Fix classifier name in HF upload.

* Reduce batch size.

* Convert the code for loading to markdown code block.

* Get kaggle username from kagglehub.whoami().

* Run black.

* Add notebook and markdown.

* Add the guide path.

* Address reivews.

* Update notebook and markdown files.

* Remove upload progress bars from the markdown file.

* Remove fine tuning progress bars from the markdown file.