Bonus items

Changelog:

1. Bonus Items system is introduced!
2. Six bonus items are spawned across the game as soon as specific conditions are met (think “Achievements”)
3. You have 8.5 seconds to pick up a bonus item before it disappears
4. Upon pick up, a bonus item grants huge amount of score and will not be spawned anymore

For more details of the six bonus items and how to get them, read this: https://tcrf.net/Bomberman_(NES)#Bonus_Items