Improve debugging, introduces `Engine::Window` + `Engine::Cursor`

[GetOutOfMyBakery]

What

Adds:

• Engine.breakpoint which accepts a block with a debugger (e.g. { binding.pry }, { debugger })
  • Can be called from anywhere:
  • with a debugger block, to break where the Engine.breakpoint { binding.pry } line has been added
  • without a block, causing a breakpoint in the main thread where the breakpoint method is defined
  • Globally defined KEY_BACKSPACE to hit a breakpoint at any point
• Engine::Window class
  • Collects all of the Window logic, and removes it from Engine.rb
  • Removes the need to pass around height and width (Game Entrypoint -> Engine.start -> Engine.open_window)
  • Ability to toggle fullscreen with KEY_F
  • Auto switches from fullscreen to windowed (and back) when hitting a breakpoint
• Engine::Cursor class
  • Handles some basics of the cursor input mode

Why

When I'm on my laptop, with a single screen, I can't hit a breakpoint and tab away from the running game. By making it easy to switch to windowed mode (and/or handling it by default when hitting a breakpoint) I can now switch between running the engine and debugging.

[!TIP] It's easy to override the default height/width/fullscreen state:

Engine::Window::MAX_WIDTH = 1440
Engine::Window::MAX_HEIGHT = 900
Engine::Window::WINDOWED_WIDTH = 1200
Engine::Window::WINDOWED_HEIGHT = 800
Engine::Window::FULL_SCREEN = false