Adds built-in shell completion support to a CommandApp.
public sealed class CompletionCommands : CommandGroup, IEnumerable
It adds:
completion <shell>: prints shell glue scripts (bash/zsh/fish/powershell).__complete: a hidden command used by the scripts to query completion candidates.kind:method, kind:property, kind:ctor. Press Esc to clear.CompletionCommands(String, String)Creates an instance of CompletionCommands.