Add support for Tracking Configuration

[justogm]

Summary

Implement a configuration system for tracking that allows users to choose:

• Tracking modalities (mouse, gaze, neither, or both)
• Tracking frequency (sampling rate)
• Enable/disable specific tracking types

Details

• Allow users to specify which input modality to track (mouse, gaze, or both).
• Configuration should include sampling frequency to control how often tracking happens.
• UI/Config file option to set preferences for tracking modalities and rate.
• Defaults and error handling if modalities are unavailable.
• Documentation updates to cover new configuration options.

Rationale

Customizing tracking is valuable for privacy, performance, and adapting to different hardware/setup constraints.