Add inference-with-keras.ipynb to PaliGemma docs (google#439)

* Add inference-with-keras.ipynb to PaliGemma docs

Adds a copy of the Inference with Keras notebook for the PaliGemma docs.

* format

* Update inference-with-keras.ipynb

Add the Apache license and copyright.

* format

---------

Co-authored-by: Mark Daoust <[email protected]>

Author: elisabandy