Swap of angles theta and phi in doc (might save some time for people to figure out)

[gigjozsa]

https://github.com/bwinkel/cysgp4/blob/f6e8dc03b5a69b3c34d2a5f97a6df1ef511697d0/cysgp4/cysgp4.pyx#L1758

This should be: distance - if sat_frame is 'zxy', or given as 'phi', 'theta', and

[bwinkel]

Thanks, @gigjozsa. I'll have a look and try to improve the docs.