Site Maintenance: Update Dependencies

[rachelwhitton]

Upgrade Site Dependencies

• Upgrade Gatsby from 4 to 5 latest version and all packages to latest version, including stale dependapot PRs which are now closed and to be consolidated within this issue:
  • #8724
  • #8617
  • #8606
  • #8602
  • #8526
  • #8368
• Resolve all Dependabot alerts and unpause dependabot

Test Coverage

MVP for this may be a test that's run locally by hand as a first iteration, but we should follow up by exploring automation opportunities with dependapot

• Add VRT coverage for each of the following paths:
  • Docs home /
  • Landing (e.g., /certification)
  • Certification study guide (e.g., /certification/study-guide)
  • Doc (e.g., /core-updates)
  • Guide (e.g., /guides/mariadb-mysql/kill-mysql-queries)
  • Release note (e.g., /release-notes/2016/01/quicksilver-platform-hooks-are-now-available)