Add Pythia xbatcher tutorial and presentation to docs

[weiji14]

Is your feature request related to a problem?

Add https://projectpythia.org/xbatcher-deep-learning/ to the tutorials page at https://xbatcher.readthedocs.io/en/latest/tutorials-and-presentations.html, and include the related presentation recording from https://discourse.pangeo.io/t/pangeo-showcase-tensors-and-back-again-xbatcher-for-filtering-resampling-and-assembling-deep-learning-model-output-october-8-2025-at-4-pm-et/5422

Describe the solution you'd like

Code should be placed somewhere here:

xbatcher/doc/tutorials-and-presentations.rst

Lines 6 to 26 in 5513cc1

	Tutorials
	---------
	.. toctree::
	:maxdepth: 1
	:hidden:
	demo
	.. grid:: 1 2 2 2
	:gutter: 2
	.. grid-item-card::
	:text-align: center
	:link: demo.html
	.. image:: https://xbatcher.readthedocs.io/en/latest/_images/demo_4_0.png
	:alt: Xbatcher demonstration
	+++
	Xbatcher demonstration

Describe alternatives you've considered

No response

Additional context

Source code is at https://github.com/ProjectPythia/xbatcher-deep-learning