[Feature] Add a nickname tag-identifier

[elhertz]

Proposed Feature Description:

Add an option to add a custom prefix for nicknamed users (to avoid impersonation and confusion)

Proposed Feature Functionality:

When someone is not using their real username and you set it so nicknamed users get a "#" prefix it would look like this:
Real username: "Robert"
Nickname: "#RobertIsTheBest"

Also allow users to use colors and formatting in their nicknames without adding the prefix (as long as they use their real username)