[DOCS] Virtual datasets

[rabernat]

We have a placeholder page on virtual datasets

icechunk/docs/docs/icechunk-python/virtual.md

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	# Virtual Datasets
	Kerchunk, VirtualiZarr, etc.

This needs to be filled in with wherever we are on virtual datasets. It's fine to put a bunch of warnings that this is all experimental, etc.

[TomNicholas]

The example from #197 would be pretty cool to have here! Even though it currently requires a few different branches...

[mpiannucci]

That is my plan, along with providing instructions for installing the branches in the github issue which will be linked