[Site Design Revamp] Add release note

[twstokes]

Description

Adds release note for the Site Design Screen Improvements project.

Testing

Verify that the note is appropriate.

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 unit tests for my changes.
• 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.

[peril-wordpress-mobile]

	Fails
🚫	Podfile: reference to a commit hash

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[antonis]

Thank you for wrangling this @twstokes 🙇
LGMT 🎉

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18785-922a7b8 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18785-922a7b8 on your iPhone

If you need access to App Center, please ask a maintainer to add you.