Implement `moderation` command or similar

Create a /moderation command that users can use to get a brief explanation of the way we use the bot (strikes) and a link to the moderation document

No file or test is named. Locate the existing command entry point and the moderation document, then add the /moderation response with a brief explanation of strikes and a link; done means users can invoke the command and receive both pieces of information.

Scritto dal modello di indicizzazione a partire dal testo della issue.