Add mainstream release NOTE blocks

[sdwheeler]

PR Summary

Fixes AB#5085 - Add mainstream release NOTE blocks

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributors guide.
• Style: This PR adheres to the style guide.

[opbld31]

Docs Build status updates of commit 6a9d3c2:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/learn/experimental-features.md	✅Succeeded	View (>=powershell-5.1)

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