Mention if a warn/ban PM has gone through

[LunaUrsa]

Many people leave privacy settings at default which means they can't get PMs from non-friends or accounts they don't share a server with which can prevent tripbot delivering the intended mod messages. We need to make it known to mods that they have not received the message

    This issue was submitted by Hipperooni 🐧 in TripSit

[silent-decibel]

I have created a PR for this. Mods will see if a DM from Tripbot to the user was successfully delivered or not