Include Qualisys SDK as optional dependency

[gemenerik]

Add qtm-rt as optional [qualisys] dependency to help users discover the required package for the Qualisys mocap example. The installation effort is the same, but now it's clear which package is needed.

Users with Qualisys systems can now install with: pip install cflib[qualisys]

[Copilot]

Pull Request Overview

This PR adds Qualisys SDK as an optional dependency to improve discoverability for users of the Qualisys motion capture system. It introduces a new optional dependency group and updates documentation to guide users on installation.

• Added qtm-rt>=3.0.2 as an optional dependency under the qualisys group
• Updated the Qualisys example documentation to include installation instructions

Reviewed Changes

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

File	Description
pyproject.toml	Adds the qualisys optional dependency group with qtm-rt package
examples/mocap/qualisys_hl_commander.py	Updates documentation with installation instructions for the new optional dependency

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