Feat: Cypress best practices docs

[dhedgecock]

📝 Cypress guidelines

• Prioritize stability - tests are only helpful when they are fast and reliable
• Use mocks for interacting with the API -> it enables deterministic failures
  • ?What about "true acceptance" testing? -> Without stability tests aren't actually helpful.

The UI should be designed to gracefully handle API failures and data failures with appropriate alerting.

• This makes the entire system faster and more robust
• Self documenting in code
• System level ownership