Add a Discord Rich presence custom mod

[cosmic blade]

@onyx mist, Please do not send any attachments which could be malicious.

[onyx mist]

The reason for adding this mod would be because some do not want the lunarclient appearing in their profile and another because of putting another discord rpc, I tried to customize the discord rpc with the Lunar Client open, but it did not work, because the lunar was with rpc active and it was overlapping my custom one.