[FEATURE] Purge by user/graim user

[luphoria]

I think a good feature to implement to graim would be purging by user/graim user. this is a pretty common feature of moderation bots and is super super useful in the event of, say, a raider. with one command you can then delete ALL of one user's messages

[luphoria]

The commit name was a typo, lol.