Add CI job to test existing kitchensink version from test runner against the new HTML

[bahmutov]

It would be nice to know if we can safely deploy the updated HTML pages without breaking the version of Kitchensink included in the Test Runner.

We could have a CI job that

• installs Cypress and scaffolds new project
• changes the scaffolded base URL to point at the local (current) HTML pages
• checks if the Test Runner stills runs

Then we know we could deploy this Kitchensink safely, the existing Cypress version will still work