v2.2.0

Changed

• Make meltingpot pip installable.
• Support import meltingpot as an alias of import meltingpot.python.
• Raise minimum Python version to Python 3.10.
• Install assets as part of pip install .
• Update Dockerfile and dev tooling (pytest, pyink, pytype, pylint, isort).
• Update examples to work with v2.
• Update README.md with new installation details.
• Migrate from rx to reactivex.

Fixed

• Remove type annotation for dtype.
• Use correct roles in play_hidden_agenda.
• Fix noop that was causing a typing error.
• Add missing __init__.py files.
• Set the default orientation to NORTH for objects that have no orientation
  defined.

Added

• Evaluation utilities.