feat: project stub for python order utilities

An empty project, with respect to functionality, but one configured with
a test framework, linters, CI integration, etc.

https://app.asana.com/0/836857747873847/839549782781239/f

python-packages/order_utils/test/test_signature_utils.py

@@ -0,0 +1,8 @@
+"""Tests of 0x.order_utils.signature_utils.*."""
+
+from zero_ex.order_utils.signature_utils import ec_sign_order_hash
+
+
+def test_ec_sign_order_hash():
+    """Test the signing of order hashes."""
+    assert ec_sign_order_hash() == "stub return value"