New methods addSubcommands and addSubcommandGroups

[Togira123]

Is your feature request related to a problem? Please describe. It doesn't look very clean when we have like 10 lines of addSubcommand, for example.

Describe the ideal solution A new method addSubcommands that takes an array of builders as a parameter. This could also be added for addSubcommandGroups.

Describe alternatives you've considered None.

Additional context None.