Fix /msg command on vanished players

[crazycat256]

Currently minecraft message commands (/minecraft:msg /minecraft:tell /minecraft:w) work on vanished players.
This PR fixes this problem by adding a MessageOptions.DisableMsgCommand option that returns an error message when someone tries to send a message to a vanished player. The error message can be customized with the setting FakeNotFound.

[rautamiekka]

Why allow customizing instead of using the vanilla ? A diff msg would tell the person the target is vanished.

[crazycat256]

Why allow customizing instead of using the vanilla ? A diff msg would tell the person the target is vanished.

If for some reason (a plugin, a version change) the default message is different, this allows you to change it (but effectively, this parameter will probably only be used very rarely).

[rautamiekka]

There has to be a way to ref it from the game itself.

[crazycat256]

I dont know

[LeonMangler]

Thank your for the PR, I appreciate the work! I don't have much time currently so it will take a while to go through all the PR's one-by-one, but I will get back to this eventually.

[LeonMangler]

This is certainly possible without accessing the command map directly. It would also need to be more configurable, e.g., by adding a list of covered commands to the config file. I have this feature in PremiumVanish and I feel like I would like to keep it as a premium-only feature, so I do not really want to copy over the working code from the premium version currently.