This is a minor update to help satisfy a user-request to optionally stop Boost giving the instruction book and main GUI item. For the GUI item it's really a bug-fix as the option was already there but not effective.

The option for the GUI item is in gui.yml as gui.buttons.main.enabled
The option for the instruction book is in messages.yml as instructions.enabled

Set both to false and Boost will no longer give those items to players.