getExtension
Returns the object that was created for the given extension.
The given name may be the name of a glTF extension, like "EXT_example_extension". If the specified extension was present in the root of the underlying glTF asset, and a loader for the specified extension has processed the extension data, then this will return the model representation of the extension.
Return
The object, or undefined
Parameters
extensionName
The name of the extension