Add VRT step to PR template checklist

[cee-chen]

Summary

See below. Now that we have Loki working locally, let's go ahead and add a step to check/update VRT screenshots to our PR template

QA

General checklist

• Browser QA
  • Checked in both light and dark modes
  • Checked in mobile
  • Checked in Chrome, Safari, Edge, and Firefox
  • Checked for accessibility including keyboard-only and screenreader modes
• Docs site QA
  • Added documentation
  • Props have proper autodocs (using @default if default values are missing) and playground toggles
  • Checked Code Sandbox works for any docs examples
• Code quality checklist
  • Added or updated jest and cypress tests
  • Updated visual regression tests
• Release checklist
  • A changelog entry exists and is marked appropriately.
  • If applicable, added the breaking change issue label (and filled out the breaking change checklist)
• Designer checklist
  • Updated the Figma library counterpart

[mgadewoll]

Good idea! 🎉