feat: sort featurecollection by area

[12rambau]

Sorting a featurecollection by area is a very common filter that one would want to apply to a collection. It's not a complicated operation but requires to well understand the concept of mapping so I decided to include it in geetools.

import ee, geetools

fc = ee.FeatureCollection("FAO/GAUL/2015/level0").limit(5)
fc = fc.geetools.areaSort()
fc.aggregate_array("ADM0_NAME").getInfo()