✨ Add initial API entry point module

This is not an `__init__.py` because it is meant to be imported
instead. Using `__init__.py` has a risk of accidentally adding
import-time computations. We want to avoid that.

src/awx_plugins/interfaces/api.py

@@ -0,0 +1 @@
+"""Entry point module for interfacing with the AWX plugin interfaces."""

tests/smoke_test.py

@@ -3,7 +3,9 @@
 It can be deleted once the project has actual tests in.
 """
 
+from awx_plugins.interfaces import api
+
 
 def test_smoke() -> None:
     """Ensure the CI picks this up."""
-    assert 'that it works'
+    assert f'that {api} works'