Add support for JPremium

[mario414x]

Describe the Feature

Hello! This is similar to the already existing support for Authme. The messages would be sended after the authentification. This is the plugin: https://www.spigotmc.org/resources/%E2%96%A0-jpremium-%E2%96%A0-authorization-plugin-%E2%96%A0-automatic-login-premium-%E2%96%A0.27766/

Provide Reasoning

This would help users which are already using JPremium. Here is the API: https://jakubson.github.io/JPremiumCleared/

Checklist

• [X] I have searched the issue tracker to ensure there are no similar feature requests
• [X] I have read the wiki to ensure this isn't already possible
• [ ] I ticked all of the boxes without actually reading them

[Insprill]

JPremium only works on proxies and doesn't appear to send any data to the backend servers, so adding support isn't possible.