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/resource/__init__.py

@@ -38,3 +38,18 @@ from .remove_resource_quantity import remove_resource_quantity
 from .unassign_resource import unassign_resource
 
 wrap_usecases(__path__, __name__)
+
+__all__ = [
+    "add_resource",
+    "add_resource_quantity",
+    "add_resource_time",
+    "assign_resource",
+    "calculate_resource_usage",
+    "calculate_resource_work",
+    "edit_resource",
+    "edit_resource_quantity",
+    "edit_resource_time",
+    "remove_resource",
+    "remove_resource_quantity",
+    "unassign_resource",
+]