Update jupyter notebook

[Janakan-S]

A functional refactor of the jupyter notebook to support grad-june instead of torch-june.

[arnauqb]

Hey, thanks for updating the notebook with the new package name. I noticed that the notebook uses hard-coded directories to where the data and config files are installed. Could you modify the notebook so that there is variable at the top that points to the grad_june installation path? Like this

grad_june_path = Path(grad_june.__file__)

then for instance we can access the config file with

config_file = grad_june_path / "configs/default.yaml"

and similar for the other paths.

Cheers