Implement /rev Command

[Heixier]

Issue Description: As a user of our Discord bot, I want to be able to use a "/rev" command to reverse any text message I send, so that I can visually confirm how it looks like when it is reversed.

Feature Description:

• The "/rev" command should take a single option: the text to be reversed.
• Upon receiving the command, the bot should reply to the user with the reversed message. For example, "/rev" with "Hello World" should make the bot reply with "dlroW olleH".
• The bot should return an appropriate error message if no arguments are provided.

Acceptance Criteria:

• The "/rev" command is successfully implemented and tested.
• Invoking the "/rev" command with a message should result in the bot replying to the user in the same channel.

Additional Notes:

• This feature will enhance the usability of our Discord bot by providing users with a convenient way to reverse messages.
• Please ensure thorough testing of the "/rev" command functionality before closing this issue.