add ECI transformation

caveat: ECI transformation error may be of order 1..10% due to rotation-only ECEF <-> ECI transform implemented.
Use AstroPy in PyMap3d for higher accuracy.

moved CI to GitHub Actions.

more singularity handling and cases tested

handle ecef2aer singularity

enu2aer OK

enu2aer OK

fix enu2aer singularity

enu2ecef OK

patch matlab precision cos(90)

more tests OK

arg consistency

BUGFIX: ecef2geodetic negative altitude

Fixed ecef2geodetic negative altitude for ECEF inside the ellipsoid.

closed form ecef2geodetic

also redid docs

Initial release

V1.0.0

non-nested test