Added anti-bot cog

[SohamGhugare]

Anti-bot cog -> Checks for invite links in user's name/nick when they join or update their nickname after joining and kicks them accordingly. Also made it so it will loop thru all the members in the server when the bot is restarted so any members left out while the bot is offline will be kicked instantly.

[BobDotCom]

A couple changes would be good here

1. make a general function, maybe like await check_user(user) and invoke that in each event. This would make the code much shorter

    @commands.Cog.listener()
    async def on_member_update(self, before, after):
        await check_user(after)

2. in your checks, it would be easier to move this code into general.py and use the check_invite function. It filters links better.

async def check_user(user):
    if await check_invite(user.display_name):
        # Take action here, user has a bad name
        pass