feat(python-generator): create output directory

Now, the output directory and its parents are created when generating
the documentation.

src/jcloud_docsgen/core/python/_core.py

@@ -1124,6 +1124,8 @@ class PythonDocumentationGenerator:
         documentation directory.
         """
 
+        self.docs_directory.mkdir(parents=True, exist_ok=True)
+
         _generate_package_namespace_documentation(
             PythonPackageNamespace('src', self.namespace()),
             self.docs_directory,