Nickname Easy

Initial release for Folia:

Features

     /nick & /unnick — players can set or clear their nickname.

     /realname — type a nickname and get the real Mojang name.

  Persistent storage — nicknames saved in plugins/NicknameEasy/nicks.yml.

  Folia-safe by design — all Bukkit/Paper API calls run on the correct region thread; background file I/O never      touches the API.