Move `environment.yml` from `files/` to `data/`

[uschille]

How could the content be improved?

The environment.yml files currently resides in the episodes/files/ folder, but it is also part of the dataset on figshare. The file may be missed when updating the figshare dataset. Since environment.yml is not used anywhere in the website, I'm leaning towards moving it to the episodes/data/ folder. Any thoughts?
@tobyhodges We looked at other lesson repositories, and there are some where it's also in episodes/files/. Any strong recommendations to keep it there?

Which part of the content does your suggestion apply to?

environment.yml