Add rate limiting

[GaurangTandon]

If we've got some decent rate limiting for the bot requests (for example, 100 requests per minute per server), we can probably release this bot for the public.
As the servers are still added manually through pull requests, there shouldn't be any issue as long as we have < 100 servers.

[Groverkss]

If this bot is in > 100 servers we have other things to worry about: https://support.discord.com/hc/en-us/articles/360040720412-Bot-Verification-and-Data-Whitelisting#what-if-im-already-in-100-guilds

[GaurangTandon]

tl;dr: we need to get our bot verified from Discord.com before we can be joined to 100 or more servers.