Update:
Hey guys so sorry for taking awhile on this update i have been working on making the boosters customizable and well everytime i've done it its broken a different part of the plugin so i thought to post this with 1 booster which is 1 hour, and then work on making a new update, so yea, sorry if the next update will take a little longer to release its only me so i will try and work on it as much as possible

Added:
Booster 1 hour
to get it its /booster give <player> <amount>

Fixed:
mobs exp on and off method not working, it now is fixed