Implementations page should list if they use the zarr format.

[TomNicholas]

#131 helps to separate the zarr "protocol" from the zarr "format". The implementations page lists libraries which read and write to the native zarr format, but it's unclear if other zarr-spec-compliant libraries belong in that table (particuarly VirtualiZarr and Icechunk, which both follow the protocol but don't use the zarr native format).

I suggest that either:

• the implementations table needs an extra column which lists what format it writes to,
• the definition of "implementation" should be clarified to mean writing to the zarr native format, and there should be a separate section on that page for other related projects