Set up flit for briar-wrapper

.gitignore

briar_wrapper/__init__.py

briar_wrapper/api.py

briar_wrapper/constants.py

briar_wrapper/model.py

briar_wrapper/models/contacts.py

briar_wrapper/models/private_chat.py

briar_wrapper/models/socket_listener.py

pyproject.toml

src/meson.build

tests/briar/api/models/test_contacts.py

tests/briar/api/models/test_private_chat.py

tests/briar/api/test_constants.py

tools/tests/test-pycodestyle.sh

tools/tests/test-pylint.sh

tools/tests/test-pytest.sh