create a new Module simpleAntenna

[OliverHasle]

Describe your use case
This module shall be part of a new functionality in Basilisk, allowing to more realistically simulate communication between a spacecraft and a ground station resp. between two spacecraft.

Describe alternatives solutions you've considered
N/A

Additional context
The simpleAntenna module shall implement a simplified antenna model, with a gaussian radiation pattern in the far field.
This module shall allow the possibility for future expansion.