Add message to requests

[super-cooper]

Description

It would be nice to give users the option to add a message to their requests to provide additional context to the admin, just like issues.

Desired Behavior

When creating a request, add a message box where the user can type a message to the admin. When viewing the request, the admin can see the message, either embedded in the request in the requests tab, or in a comment thread similar to Issues. I believe the former would be far easier to implement than the latter.

Additional Context

This would be helpful to me because sometimes users want to queue something on the backlog, and sometimes they want to watch their request right away. Having these messages to provide helpful context is far easier for me to work with as an admin in contrast to my current strategy: messaging the users on Discord when they make requests.

Code of Conduct

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