• engine: Added concept of lod bias to materials.
  [⚠️ Materials need to be rebuilt to access this new feature].
• engine: Fix, BGRA ordering respected for external images with OpenGL on iOS.
• engine: Use more sensible defaults for spot light inner outer cone angles.
• gltfio: Improved handling of transparent materials.
• Metal: Fix potential crash on earlier versions of iOS (<= 13.0).
• Android: Fix filament-utils-android 'lite' flavor.
• Java: Fix potential crash with IBLPrefilter.