Implemente este método para mostrar información asset encima de la pre-visualización del asset.
You will also have to implement HasPreviewGUI and OnPreviewGUI in addition to this method.
The default implementation just returns an empty string, which disables the feature.
Note: Inspector previews are limited to the primary editor of persistent objects (assets), e.g., GameObjectInspector, MaterialEditor, TextureInspector. This means that it is currently not possible for a component to have its own inspector preview.