Feature: Post Startup Message

[lcox74]

We currently determine Tony's operational status by observing if the bot user appears online upon startup. However, enhancing user feedback would be beneficial by implementing a feature where Tony announces its startup within a designated Discord channel. This can be accomplished by integrating a message posting function within the func(s *discordgo.Session, event *discordgo.Ready) event handler, ideally situated in the main.go file. Below is a proposed syntax for initiating this feature:

func main() {
    db := database.NewDatabase("tony.db")

    // Instantiate a new bot
    bot, err := framework.NewBot(token, serverId, db)
    if err != nil {
        log.Fatalf("Error while creating bot: %s", err)
        return
    }

    bot.OnStartup(startupCb)
}

func startupCb(s *discordgo.Session, event *discordgo.Ready) {
    // Implementation details here
}

For improved flexibility and to adhere to best practices, the channel in which Tony posts the startup message should be configurable via an environment variable named DISCORD_STARTUP_CHANNEL, with the default channel being tony-dev.

Furthermore, enhancing this startup message to include the bot's current version and a changelog for that version would greatly benefit our users by keeping them informed about new features and fixes.