specify exported api methods in __all__

It's py.types requirement, similar to 6e2edbf

Example issue without __all__:
import ifcopenshell
import ifcopenshell.api.project

# "create_file" is not exported from module "ifcopenshell.api.project"
ifcopenshell.api.project.create_file()

src/ifcopenshell-python/ifcopenshell/api/grid/__init__.py

@@ -30,3 +30,9 @@ from .create_grid_axis import create_grid_axis
 from .remove_grid_axis import remove_grid_axis
 
 wrap_usecases(__path__, __name__)
+
+__all__ = [
+    "create_axis_curve",
+    "create_grid_axis",
+    "remove_grid_axis",
+]