Site Editor: Navigation Sidebar Sliding Animation

[Copons]

Currently, when the Site Editor's navigation sidebar slides in, the rest of the content immediately repositions instead of sliding along with the sidebar:

The sidebar and the content should both animate and at the same time.

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For reference, the sidebar slide is composed by two different animations:

• The sidebar itself transitions from transform: translateX(-100%) to transform: translateX(0).
• The toggle button transitions from width: 60px (size of the WP/site icon) to width: 300px (size of the sidebar), after a brief delay to sync it with the sidebar animation.