Closes #3404: Add release notes section to PR template

[danahertzberg]

Description

Adds a section for Release notes in the PR template

Related issues

Closes #3404

How to test

Review template for changes

Types of changes

Arizona Quickstart (install profile, custom modules, custom theme)

• Patch release changes
  • [ ] Bug fix
  • [ ] Accessibility, performance, or security improvement
  • [ ] Critical institutional link or brand change
  • [ ] Adding experimental module
  • [ ] Update experimental module
• Minor release changes
  • [ ] New feature
  • [ ] Breaking or visual change to existing behavior
  • [ ] Upgrade experimental module to stable
  • [ ] Enable existing module by default or database update
  • [ ] Non-critical brand change
  • [ ] New internal API or API improvement with backwards compatibility
  • [ ] Risky or disruptive cleanup to comply with coding standards
  • [ ] High-risk or disruptive change (requires upgrade path, risks regression, etc.)
• Other or unknown
  • [x] Other or unknown

Drupal core

• Patch release changes
  • [ ] Security update
  • [ ] Patch level release (non-security bug-fix release)
  • [ ] Patch removal that's no longer necessary
• Minor release changes
  • [ ] Major or minor level update
• Other or unknown
  • [ ] Other or unknown

Drupal contrib projects

• Patch release changes
  • [ ] Security update
  • [ ] Patch or minor level update
  • [ ] Add new module
  • [ ] Patch removal that's no longer necessary
• Minor release changes
  • [ ] Major level update
• Other or unknown
  • [ ] Other or unknown

Checklist

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.