v0.3.0

Added

• Asynchronous Task<T> to load assets without blocking.
• OpenGL back-end releases textures properly now.
• Add a IGE_DEBUG CMake option to enable/disable some debug-only assertions.

Changed

• AudioClip is now loaded with AudioClip::load or AudioClip::load_async
  instead of its constructor.

Removed

• Removed AudioClip constructor taking an audio file path.

Fixed

• Unnecessary compilation of generated files when re-configuring CMake.