| key | The key of the existing GUIContent. |
| text | The text associated with the GUIContent.text. |
| tooltip | The tooltip to display when the cursor hovers over the icon. |
| icon | The icon to associate with the GUIContent.image. |
| iconName | The name of the icon. |
Gets the GUIContent from the Unity built-in resources with the given key or creates a GUIContent for a GUI element.
The text and the tooltip are localized and loaded with an icon.
Typically, the icon from `Assets/Editor Default Resources/Icons` is fetched using the icon name. Only the name of the icon, without the .png extension is needed.