🎨 Add figure showing xbatcher's features for slicing n-dim arrays

[weiji14]

Illustration of xbatcher's features of slicing multi-dimensional arrays on-the-fly with named variables.

This is useful for e.g. time-series or multi-variate oceanography / climate model outputs. Diagram on the left shows how a datacube is sliced, and code block on the right shows how regular slicing code compares to xbatcher.

At the bottom, more features are mentioned such as lazy loading, xarray acessors, and the experiment cache mechanism. Also mentioned upcoming roadmap like shuffling/sampling utilities and async loading of batches.

References:

• https://doi.org/10.6084/m9.figshare.22264072.v1
• https://xbatcher.readthedocs.io/en/latest/roadmap.html
• Link to edit on Excalidraw - https://excalidraw.com/#json=4iuB5hMt9ihbLNrN8Pirw,Ktfz9P8oHqQS5IJrBzoC8A