Config & Java

This version has been compiled with Java 16 and will most likely not work with older versions of Java.
I recommend you to update as soon as possible.

You can find more information on how to do that on PaperMC wiki:
https://papermc.io/forums/t/java-16-mc-1-17-and-paper/5615

Changed HideButtonsOnSinglePage config option to AlwaysShowPageButtons.

If set to true - it will displays Next and Previous page buttons at all times, in other case - buttons will only be displayed if there's a Previous or Next page.

Did some major code refactoring, which should increase the performance ever so slightly.

Added more PlaceholderAPI support.