add notebook to demonstrate patch saving in tfrecord format

[quantumjot]

Would be good to have a notebook that takes patch images and writes them out as a tfrecord file for training the VAE.

[quantumjot]

We should use the cellx library for this:

https://github.com/quantumjot/cellx/blob/53015f8a45c8fc7236fe382431f8f55f6edf08c4/cellx/tools/dataset.py#L24-L37