Big bug-fixes

So, where should I begin? We decided to fix some bugs that we'd picked up during production.

- We sorted out the FPS. At least, we hope so! Use the ready-made Windows and Linux builds, please.

- We fixed the boss's spawn. Now he regularly appears and attacks. Try to defeat him.

- Balanced some indicators to make the game more interesting.

- Added menus for the main screen, death and finale. 

- The build for Windows and Linux has been made available to everyone. It's a small victory for us.

This is a great chance for us to try something new. Our team has never done anything like this before. Thank you #32BitGameJam for giving us the opportunity to test ourselves in this field.