PR: Add the *Color Interop Forum* (CIF) recommendation *RGB* colourspaces.

[KelSolaar]

Summary

This PR adds the Color Interop Forum (CIF) recommendation RGB colourspaces.

References #1312.

Preflight

Code Style and Quality

• Unit tests have been implemented and passed.
• Pyright static checking has been run and passed.
• Pre-commit hooks have been run and passed.
• [N/A ] New transformations have been added to the Automatic Colour Conversion Graph.
• New transformations have been exported to the relevant namespaces, e.g. colour, colour.models.

Documentation

• New features are documented along with examples if relevant.
• The documentation is Sphinx and numpydoc compliant.