GitHub Markdown now support an option to highlight a "Note" and "Warning" using blockquotes

PR Summary

• Fix the syntax of README.md to support the new interface, to highlight notes with blockquotes: https://github.com/orgs/community/discussions/16925

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure you've added one or more new tests
• Make sure you've tested these changes in terminals that PowerShell is commonly used in (i.e. conhost.exe, Windows Terminal, Visual Studio Code Integrated Terminal, etc.)
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed at PowerShell-Docs
    • Doc Issue filed:

Microsoft Reviewers: Open in CodeFlow