Add release notes for Unified Dashboard

[zwarm]

This PR adds release notes for Unified Dashboard - Jetpack Only

• [**] [Jetpack-only] Update the main site navigation on the My Site screen, making it easier to access the common site sections. The new shortcuts can be modified using the Personalize Home Tab screen. [https://github.com/Unified Dashboard: Remove tabs and update quick links layout #19151]

cc: @oguzkocer

To test:
Nothing to test

Regression Notes

1. Potential unintended areas of impact N/A
2. What I did to test those areas of impact (or what existing automated tests I relied on) N/A
3. What automated tests I added (or what prevented me from doing so) N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

UI Changes testing checklist: N/A

[peril-wordpress-mobile]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone

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