Version update - 2021.1.6 * Added a new `PythonContextMenuItem` class inheriting `ContextMenuItem` which takes python_function and converts it to an executable command. * Added type hints and argument documentation for most of the methods. * Added `.create_for`, `.delete` and `.delete_for` methods for `ContextMenuItem` and `ContextMenuGroup`. * Updated usage example in __main__. * Updated README.md to reflect the changes.