Add the ability to merge properties into entity definitions

## 🪤 Context

Need a spot on the UI to provide properties that will be merged with entity attributes.

Entities may not always have the desired attributes available when the `type-writer` code scans them. This would provide some type definitions that could be merged in with the entity to provide a more consistent picture of what is a valid type for it

## 📬 Caveats

## 🩻 Additional details