Add heating models for nanoflare trains

[wtbarnes]

It would be useful to have a function that generated an event list for a series of events, say with a specified interevent spacing. This could be either uniform or based on some distribution. The same could be true for the heating rate of each event as well.

As an example, see the code here: https://github.com/wtbarnes/synthesizAR/blob/main/synthesizAR/interfaces/ebtel/heating_models.py