add pyproject.toml

[rb-synth]

• Can now clone and pip install -e . or add as github dependency.
  • Can import from other python scripts with from syncnet.run_all import run_all etc.
• Can run run_all.py to get a single value for mean distance (without shift, useful as quality metric).
• Use temporary directory for computing results
• Download script to out-of-source location
• Tidy and make more pythonic. Something like black should still be run.