Akimbo Update

Hey! It's Jerem this time; couldn't find Speaker Guy. Maybe he's busy helping new players again?

Here's the bulk of the latest update:

1. "Akimbo Upgrade" to replace "Skip Wave" purchase. Double the gun? Double the pun!
2. Final wave! There are two significant mystery changes in wave 10 on top of the usual health and duration buffs. Credits were unnecessary so I made something else neat for the end. :)
3. Price and purchase rework. Prices have been further reduced and after a purchase the menu closes. Choose carefully!
4. Shop aesthetic upgrade. Niiiiice.
5. Wave 2 completion unlocks gun upgrades.
6. Minor audio fixes. Pepew!
7. Minor hitbox adjustments. 
8. Created a quit confirmer, got a fair few requests for this feature.

I wish you all the best! Thanks again to those who have been so kind with your feedback!