add a main module

src/bmipy/__init__.py

@@ -1,7 +1,7 @@
 """The Basic Model Interface (BMI) for Python."""
 from __future__ import annotations
 
-from ._version import __version__
-from .bmi import Bmi
+from bmipy._version import __version__
+from bmipy.bmi import Bmi
 
 __all__ = ["__version__", "Bmi"]

src/bmipy/__main__.py

@@ -0,0 +1,6 @@
+from __future__ import annotations
+
+from bmipy.cmd import main
+
+if __name__ == '__main__':
+    raise SystemExit(main())