- Fix lights being overly strong due to an excessive range,
  which led to clustering artifacts.
- Make VoxelGI and SDFGI brighter to make the scene more readable.
- Tweak spotlight colors to better match their emitter material.
- Make the core light orange-red to make it look more "unique" in the scene.
- Add window mode, V-Sync and FPS limit options.
- Add resolution scale and scale filter options (bilinear, FSR1, FSR2).
  The default is to use FSR2 at native resolution to provide high-quality
  temporal antialiasing.
- Add volumetric fog (enabled by default), used as a volumetric lighting
  solution.
- Add SSIL option (disabled by default), which helps better ground some
  objects in the scene.
- Refactor settings code to use ConfigFile instead of manual JSON serialization.
- Reorder settings to feature video settings first, then rendering settings.
- Order settings from least expensive to most expensive.
- Add performance color hints for settings
  (green = fast, yellow = average, orange = slow, red = slowest).
- Add volumetric fog and a fake bounce light to the menu.
- Make all setting changes effective in the menu.
- Tweak shadow settings to improve performance and visual consistency.
- Render GI at full-resolution to improve temporal stability when using
  FSR2 or TAA. Using upscaling should be preferred instead,
  since this demo relies on strong GI effects to look good.
- Improve menu theming using the StyleBoxFlat Skew property.
- Use the `canvas_items` stretch mode to match 3.x demo behavior, which
  used the `2d` stretch mode but wasn't ported over by the project converter.
- Only display multiplayer ID in the debug menu if currently online.
- Fix menu not using `experiment.hdr` for reflections as intended.
- Remove unused menu button textures (these were replaced by StyleBoxFlat
  in the 4.0 port).