[+] Add 1.21.4 support.
[+] Fix database leak issue.
[+] Improve database system.
[+] Complete recode of the plugin, increasing the modularity aspect so it's easier to make a new update without breaking the code.

I have decided to make NextGens open-source which can be accessed at https://github.com/mdaffa48/NextGens/ hoping other developers could contribute and thus helped to fix bugs or add new features.