Returns if the weapon is in burst mode.
Only the Glock and Famas can return 1 as they are the only guns in the
game that have a burst fire mode.
This native does not verify that the provided entity is a weapon
entity. It will return incorrect values for non-weapon entities.
1 if the weapon is in burst mode, 0 otherwise
If an invalid entity index or a client index is provided,
an error will be thrown.