Update docs on virtual references to match VirtualiZarr v2.0's updated API#1099

TomNicholas wants to merge 6 commits intoearth-mover:mainearth-mover/icechunk:mainfrom

TomNicholas:update_virtualizarr_docs_for_v2TomNicholas/icechunk:update_virtualizarr_docs_for_v2Copy head branch name to clipboard