follow-up tasks for `explore`

[keewis]

At the end of #67, I posted a list of things to do to improve the method:

• figure out how to install arro3-core from conda-forge on osx-arm (install arro3-core from conda-forge #78)
• add a legend to the map
• implement sliders for multidimensional data (support plotting multi-dimensional data #124)
• use the constructor methods of geoarrow.rust once they are available on a released version
• support non-standard names for the cell id coordinate
• allow customizing the coordinates included in the hover table (allow specifying additional coords to include in the pixel inspection table #123)
• tests
• support for dataset plotting
  • per-variable colorization params