Add Report System on Philbot

[royh02]

Ported over from TODO spreadsheet

Create a report command !report using slash commands

[dlzou]

The idea is to let users DM PhilBot with the ID of message in question, then PhilBot would copy the message to a moderator channel where mods decide if the message violates a rule. If in violation, the poster of the message is set to read-only for a period of time depending on number of offenses. Blatant misreports, however, can lead to a read-only period for the reporter.

There's quite a bit of logic involved, plus at least 2 columns would need to be added to the Discord database, hence the hard label. This issue is also not a priority at the moment, as the server seems well under control.