Suggested file location to write the new backup.
Note that your extension is free to ignore this and use its own strategy for backup.
If the editor is for a resource from the current workspace, destination will point to a file inside
ExtensionContext.storagePath. The parent folder of destination may not exist, so make sure to created it
before writing the backup to this location.
Generated by TypeDoc
Additional information used to implement {@linkcode CustomEditableDocument.backup}.