Move datasets used on documentation cite under the Kandy project

[zaleslaw]

https://kotlin.github.io/kandy/simple-usa-states-polygons-geojson.html

For example:

val usaStates =
    GeoDataFrame.readGeoJson("https://raw.githubusercontent.com/AndreiKingsley/datasets/refs/heads/main/USA.json")

usaStates.plot {
    geoPolygon()
}