Add explanation for light-time corrections

[ChristopherRabotin]

Description

When trying to summarize how aberrations work in ANISE, I when to the website and could not find anything other than some documentation on the API itself. That did not help me understand why querying a spacecraft's position at the start of its ephemeris with LT enable responded that no position data was available.

This documentation should be mimicked, and should reference, https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/abcorr.html .

Documentation type

• Explanation

Affected area(s)

https://nyxspace.com/anise/reference/api/python/#class-aberration -> this is what I used
There was nothing in here: https://nyxspace.com/anise/explanation/

In the best of all worlds, the exception itself would specify additional context (and that should be possible with SNAFU).