feat: add basic displays for widgets (#356)

* feat: add widgets for making ATL08 PhoREAL requests
* feat: add full screen control option for leaflet map
* feat: add static method for default mosaic fields
* fix: replace deprecated `pkg_resources` with `importlib`
* refactor: leaflet scatter as accessor to geodataframe
* refactor: ICESat-2 transect plot as accessor to geodataframe
* refactor: can enter atl03 fields as ICESat-2 transect geodataframe accessor