Issue #875
Read newDocument
This method calls openUntitledDocumentAndDisplay(_:).
Read openUntitledDocumentAndDisplay
The default implementation of this method calls defaultType to determine the type of new document to create, calls makeUntitledDocument(ofType:) to create it, then calls addDocument(_:) to record its opening.
Read defaultType
The default implementation of this method returns the first Editor type declared by the CFBundleDocumentTypes array in the application’s Info.plist, or returns nil if no Editor type is declared. You can override it to customize the type of document that is created when, for instance, the user chooses New in the File menu.