[Feature Request] Allow custom value returns from Item ChoiceSet RE

[Antmanton]

When selecting a ChoiceSet of items from OwnedItems or a compendium filter, it would be useful to be able to specify a custom return object based on the selected item's properties instead of just the item id, using a value property like for custom choice objects. This could be used to retrieve and export field values from a source item to implement things like Blazons of Shared Power.

Suggested syntax might be something like this, combined with appropriate WeaponPotency and Striking REs:

{
  "choices": {
    "ownedItems": true,
    "predicate": [
      "item:usage:hands:1",
      "item:magical"
    ],
    "types": [
      "weapon"
    ],
    "value": {
      "id": "{choice|_id}",
      "striking": "@choice.system.runes.striking",
      "potency": "@choice.system.runes.potency"
    }
  },
  "adjustName": false,
  "flag": "weapon",
  "key": "ChoiceSet",
  "prompt": "PF2E.SpecificRule.Prompt.Weapon"
}