+'BeforeWelcomeCreation': before the welcomecreation message is displayed to a newly created user
+&$welcome_creation_msg: MediaWiki message name to display on the welcome screen to a newly created user account
+&$injected_html: Any HTML to inject after the "logged in" message of a newly created user account
+
+'BitmapHandlerTransform': before a file is transformed, gives extension the
+possibility to transform it themselves
+$handler: BitmapHandler
+$image: File
+&$scalerParams: Array with scaler parameters
+&$mto: null, set to a MediaTransformOutput
+