Support damage for non-attack actions

[rg-wood]

Add support for damage and attack bonuses for non-attack actions, and spell-like actions.

For example, the action:

{
    "name": "Shadow Rift (1/day)",
    "id": "shadow-rift",
    "description": "The Gloaming Queen can open a rift to the abyss in a 20-foot sphere centred on a point she can see within 120 feet. Any creature within the rift takes 10d8 necrotic damage, or half damage with a successful DC 14 Constitution saving throw."
  }

There should be a method to define the damage and saving throw for this action so that CR can be correctly calculated.