Attribute used to register a class as an overlay.
Overlay must derive from the Overlay class.
| defaultDisplay | Set this value to true to ensure that the target Overlay will be shown when a new instance of the EditorWindow type is instantiated. |
| displayName | Defines what the display name of the overlay will be. |
| editorWindowType | Defines which EditorWindow type the overlay will be used in. |
| id | Defines the unique identifier used to identify the overlay. |
| ussName | Name of the overlay's root visual element. |
| OverlayAttribute | Attribute used to register a class as an Overlay. |