Permission-based chat radius

[takatalvi]

Hi, I would like to suggest another enhancement to EssentialsXChat, and that is permission-based chat radius. Currently when a chat radius is used, it affects all players equally, even though some permissions allow a way around it. The same way as there are separate chat formats for each group, servers could benefit from having separate chat radiuses for different groups, either to emphasize their ranks (in case of servers with a multi-level hierarchy), or to make chat in events/games separate, or to create a more immersive system of chat-based punishments. Thanks!

[mdcfe]

Going to unassign myself from this as I currently don't have the time to work on new features, but anyone's welcome to implement this in a PR.

My preferred solution for this would be to use permissions meta, as this is an ideal place to store per-user or per-group settings. This would require adding methods to read meta to the permissions abstraction, but is otherwise very doable. It would also be good to add a comment in the config.yml explaining that you can use permissions meta for per-group settings (and eventually a wiki page, once the wiki infrastructure is sorted).