Add .readthedocs.yaml configuration file
As described in https://blog.readthedocs.com/migrate-configuration-v2/ we will need a configuration file if we want the documentation to be built by readthedocs in the future.
As described in https://blog.readthedocs.com/migrate-configuration-v2/ we will need a configuration file if we want the documentation to be built by readthedocs in the future.
