Add the ability to create aliases for subcommands#62

In this case: ```python # clipstick_cmds.py from clipstick import parse from pydantic import BaseModel class AlfaCmd(BaseModel): """Hacer cosas de alfa""" uno: str """Parámetro para alfa""" def run(self): print(f"alfa {self.uno}") class BetaCmd(BaseModel): """Hacer cosas de beta""" dos: str """Parámetro para beta""" def run(self): print(f"beta {self.dos}") class CmdApp(BaseModel): """Herramienta de test""" subcmd: AlfaCmd | BetaCmd def run(self): self.subcmd.run() if __name__ == "__main__": app = parse(CmdApp) app.run() ``` the resulting app returns this to the help request: ```bash $ python clipstick_cmds.py -h Usage: clipstick_cmds.py [Subcommands] Herramienta de test Subcommands: alfa-cmd Hacer cosas de alfa beta-cmd Hacer cosas de beta ``` The command name is taken from the class name. It would be useful to have the ability to add one or more shorter or different alias(es) to the commands.