Coloraide-extras

- **FIX**: Fix issues with spectral interpolation.

- **FIX**: Fix issue with how spectral interpolation concentrations are clipped.

- **NEW**: Drop Python 3.8.
- **NEW**: Require ColorAide 4.3.
- **NEW**: Add spectral interpolation that leverages Kubelka-Munk theory for color mixing.

- **NEW**: Officially support Python 3.13.
- **NEW**: Require ColorAide 4.0.

- **NEW**: Officially support Python 3.12.

- **NEW**: Drop Python 3.7.
- **NEW**: CIE 1960 UCS moved to official ColorAide repository.