Warn if running download outside expected dir

[DavidFair]

(More of a nit / user improvement)
Currently sciml-bench works on the assumption a user is already in the git repo when running a download.

In this case the machine rebooted, then I re-ran the download which ended up in the wrong directory.
A simple check that sciml_bench exists in the current working dir, with a warning to nudge people that you expect them to be in the source/git directory would help.

[samueljackson92]

Hi David, the datasets should be downloaded to dataset_root_dir in the config.yml. This is by default in the user home directory ~/scml_bench/datasets. For me, if I cd to another directory and run a download it still puts it in the correct place?

Perhaps can you provide more info as I cannot reproduce the issue you're seeing?