Add a SphericalAxis function

[aplavin]

Currently, as I understand from earlier discussions with @asinghvi17, GeoAxis assumes some ellipse/geoid for the shape, and takes coordinates in degrees. I (and others in astronomy) typically want to plot a regular sphere, with native units (radians) for lat/lon.
I've been using this snippet (again, adapted from @asinghvi17 recommendations):

SphericalAxis(args...; kwargs...) = GeoAxis(args...; 
	source="""
	GEOGCRS["WGS 84",
	    DATUM["World Geodetic System 1984",
	        ELLIPSOID["WGS 84",6378137,298.257223563,
	            LENGTHUNIT["metre",1]],
	        ID["EPSG",6326]],
	    PRIMEM["Greenwich",0,
	        ANGLEUNIT["radian",1],
	        ID["EPSG",8901]],
	    CS[ellipsoidal,2],
	        AXIS["geodetic latitude (Lat)",north,
	            ORDER[1],
	            ANGLEUNIT["Rad",1]],
	        AXIS["geodetic longitude (Lon)",east,
	            ORDER[2],
	            ANGLEUNIT["Rad",1]]]
	""", kwargs...,)

There is quite some magic here, but it works :) Can such a function be added to GeoMakie?