Title and menu screens

[paulbrzeski]

Objectives:

• Implement support for multiple scenes
• Introduce title screen with logos
• Introduce menu screen with options from current menu
• Implement some kind of development back door for auto selecting gameplay mode and skipping title and menu sequences

[paulbrzeski]

• Langenium #31
  • Investigating UI options
    • Probably best to use https://github.com/felixmariotto/three-mesh-ui
  • Reviewing old static scene loader and how to weave that in
    • Looks like v6 architecture is already on it's way, but it needs more uncoupling so that there's something to route scene requests.
    • Main.js needs more refactoring
  • Might need to park this for now and go back to #33 / PR #30 as that's changing how postprocessing works and those are currently attached to the scene

[paulbrzeski]

Need to add help screens as well