PR: Add missing RGB colourspaces in documentation.

[MrLixm]

Hello, minor documentation fix suggested.

Summary

Fix documentation by adding missing colorspaces. Missing colorspaces where retrieved by comparing the documentation against the list of colorspaces defined in colour.RGB_COLOURSPACES.

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.
• [x] New transformations have been added to the Automatic Colour Conversion Graph.
• [x] New transformations have been exported to the relevant namespaces, e.g. colour, colour.models.

Documentation

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

[KelSolaar]

Thank you @MrLixm!