feat: Excalibur Scene Transitions & Loaders

[eonarheim]

===:clipboard: PR Checklist :clipboard:===

• 📌 issue exists in github for these changes
• 🔬 existing tests still pass
• 🙈 code conforms to the style guide
• 📐 new tests written and passing / old tests updated with new scenario(s)
• 📄 changelog entry added (or not needed)

==================

This PR implements an API inspired by https://github.com/mattjennings/excalibur-router/ with permission from Matt.

The idea behind this refactoring is to add transitions between scenes and scene specific loaders!

• Add or remove scenes by constructor
• Add loaders by constructor
• New DefaultLoader type that allows for easier custom loader creation
• New Transition type for building custom transitions
• New scene lifecycle to allow scene specific resource loading
  • onTransition(direction: "in" | "out") {...}
  • onPreLoad(loader: DefaultLoader) {...}
• New async goto API that allows overriding loaders/transitions between scenes
• Scenes now can have async onInitialize and async onActivate!
• New scenes director API that allows upfront definition of scenes/transitions/loaders

View this file for a current example of what the API looks like

Defining scenes upfront

const game = new ex.Engine({
  scenes: {
    scene1: {
      scene: scene1,
      transitions: {
        out: new ex.FadeInOut({duration: 1000, direction: 'out', color: ex.Color.Black}),
        in: new ex.FadeInOut({duration: 1000, direction: 'in'})
      }
    },
    scene2: {
      scene: scene2,
      loader: ex.DefaultLoader, // Constructor only option!
      transitions: {
        out: new ex.FadeInOut({duration: 1000, direction: 'out'}),
        in: new ex.FadeInOut({duration: 1000, direction: 'in', color: ex.Color.Black })
      }
    },
   scene3: ex.Scene // Constructor only option!
  } 
})

game.start('scene1',
{
  inTransition: new ex.FadeInOut({duration: 500, direction: 'in', color: ex.Color.ExcaliburBlue})
  loader: boot,
});

[github-actions]

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[eonarheim]

Woooo! Finally!