[Spike] - Research options for visual regression tests

[grahamlangford]

Goals

• Reduce the risk of visual regressions making their way into production
• Shorten feedback loops
  • Rainforest currently provides all visual regression testing, but we aren't alerted quickly enough
  • Rainforest could still be the solution, if we are able to improve alerting
• See https://www.notion.so/pixiebrix/Release-1-8-13-429913196b1d4d42b5e9a19f30ba3cdf

Acceptance Criteria

• [ ] Document suggestions for changing or improving the way we perform visual regression tests
• [ ] Share out suggestions with engineering team for discussion/decision (possibly a brownbag?)