refactor(apps/discord-bot): update command package

[rasitds]

Commands separated.

• /set streamer -> /set-twitch streamer
• /delete streamer -> /del-twitch streamer

Command and option names updated.

• /set -> /set-twitch
• /delete -> /del-twitch Renamed channel-name option to channel

Command function and file names updated.

• invitecommand.go -> invite.go
• UpdateCmdCommand() -> UpdateCommandCommand()