`commandflow-discord` should use Application commands

[yusshu]

commandflow-discord currently uses messages to detect commands. We should use Application Commands instead since it's a more user-friendly and native way to create bot commands.

Also, bots can't read message contents without a privileged intent

[FixedDev]

Yeah, it should be done that way, it’s only programmed like that since the module predates discord application commands, but this should be worked on