Update readthedocs config to use dependency groups

[RalfG]

Fixed

• Fixed ReadTheDocs installation by using new dependency groups instead of old optional dependencies.

[Copilot]

Pull Request Overview

This PR updates the ReadTheDocs configuration to use the new PEP 735 dependency groups syntax instead of the deprecated optional dependencies (extras_require) approach. The version is also bumped to include a post-release identifier.

Key changes:

• Migrated ReadTheDocs build configuration from python.install with extra_requirements to build.jobs.install with pip install --group
• Updated package version to include post-release suffix

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
pyproject.toml	Version bumped to 3.2.0.post1 to reflect configuration fix
.readthedocs.yml	Replaced deprecated extras-based install with dependency group syntax for docs installation

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