feat: dev expyriment version + uuid

[mhaeming]

• Set a UUID4 as the subject_id
• FlankerExperiment.py was autoformatted using Ruff
• Added the development version of expyriment to the requirements.txt as the latest stable release does not build for me on Linux
  • This might be a little broken upstream, as some images are not in the correct location. Please let me know if this affects you.
    • Current Workaround: Copy the files manually into the required folder
    • I might contribute a change directly to expyriment for that or create a custom fork
• Replaced sklearn with scikit-learn in requirements.txt to avoid deprecation warning
• Added a .gitignore file for the .xpe and .xpe files