Add Support for Images to the Core Entity Types

[VarunS1997]

All of the core entity types should now be allowed to have images.

That means:

• Abilities
• Feats
• Items
• Heritages
• Spells

But because we want to do #62, we should hold off on this until that's done.

[VarunS1997]

Completed, and part of 2024.06.02.

The following now support images: Abilities, Campaigns, Feats, Heritages, Items, Item Properties, Lore, Casting Method Modifications, and Spells