It is important to be able to read online the documentation for different versions. Currently there seem to be no way to access different versions of the documentation. It needs to be implemented especially because API will evolve and people should be able to have access to previous versions of the API too.

Look for instance pylops or jax. It's easy to select the version (at the bottom of the left menu). And you can also read previous versions.

Not sure it requires to be on readthedocs though.