[FEATURE] Gun upgrades

[maxogod]

🚀 Feature

Upgrades for the lasers

Motivation

To allow the player to have a better chance at surviving late game.

Implementation

• tri-laser
• golden laser (x2 damage)
• rainbow laser (x3 damage) -- one guaranteed at some point during the boss fight
• immunity cloak (immune - pulsing for a few seconds)
• Extra ideas?

Additional context

Probability of spawns for each upgrade - TBD