Provide guidance and improve usability of search and subset request over poles

[asteiker]

From Hackweek tutorial feedback, it was suggested to add clarification on how to request data over the poles, either in helper notebooks or within icepyx itself, including guidance on the input coordinate order for icepyx/nsidc bounding_box. David Shean suggested adding support for something like the standard bounds object (or other bounding box object) in shapely/geopandas/rasterio? Or a dictionary object {‘minx’:-102, ‘miny’:-76…})