CI regression testing - Githubissues

This is the initial work to have CI regression testing in place for our notebooks, implements a build workflow in Github for Windows, OSX and Linux so in the near future we can automate testing and rendering of the tutorials. The following changes have been made:

import verification:
- A script will verify that any library used in our notebooks is indeed included in our default environment
pinned environment:
- we're now using conda-lock for the different platform, this is complementary to Docker which remains as the preferred workflow.
individual tutorial environments:
- on top of the monolithic Docker image and conda environment we are now providing per-tutorial environments, this has some benefits for reproducibility and avoid potential conflicts with the base environment in the future. There is still some deliberation on how we should approach the creation of new tutorials, i.e. work with the base environment and branch out only if there is a conflict.

IceFlow

The Hermes endpoints are still broken but a hack in the OAuth2 calls fixed the authentication so we can place orders again in Hermes/Valkyrie.
There were some changed required in the widget, I think eventually this should be a library on its own.

nsidc / NSIDC-Data-Tutorials

CI regression testing #42