Setup GitHub CI with Cypress and Pytest

I think it would be a great idea to implement some cypress testing, it is really needed to ensure that the application is working well.

External PRs aren't configured to run CI on this repo, but you can see the green checkmarks on my fork

Set up a new tests directory for everything test-related, with subdirectories by language: one for python, one for node.
Set up Cypress with a very minimal test. (Alternatively, package.json could have been added at the top level, but that might have been distracting.)
Move existing python test to new subdirectory, and tweak so they run: fix import, and add missing parameter.
Test run creates a new pickle file at the top level: Simplest fix is to just gitignore; Alternative would be not to output this file.
Add workflows to run Cypress and Pytest on CI.
- I have only used actions for checkout and language install. There are more sophisticated actions (for Cypress, for example) that reduce the code needed in the workflow... but they also hide the details that are needed to replicate the action locally.
- I'm running pytest with -m; The alternative would be to set the path explicitly: PYTHONPATH='.' pipenv run pytest

Next steps:

Improve Cypress test coverage. (At least hit every tab... Let me know if any particular features are brittle and can use more testing.)
Use CI to confirm Black style. (Several files currently have extra white space.)
Configure Cypress workflow to save video of failing test runs for two or three days?
Single script to run all tests locally for convenience?
Add linting to CI to supplement the style checking from Black. (Probably Flake8.)
Upgrade dependencies: The original motivation for adding tests.

CenterForTheBuiltEnvironment / clima