Site Editor: Move Styles to top of sidebar navigation

[himanshupathak95]

Fixes: #68576

What?

Move the Styles navigation item to the top position in the Site Editor's main sidebar navigation, before Navigation, Pages, Templates, and Patterns.

Why?

The current hierarchy of the main menu feels unbalanced. "Styles" is a global customization tool that affects the entire site, unlike other sections that manage specific entities. Moving it to the top:

• Better aligns with the editor's description: "Customize the appearance of your website using the block editor"
• Creates a clearer distinction between global tools and entity management
• Improves accessibility to this frequently used feature

Testing Instructions

• Navigate to Site Editor (Appearance > Editor)
• Verify Styles appear at the top of the navigation menu
• Click each navigation item to ensure they all work as expected

Screenshots

Before	After

Screencast

Screen.Recording.2025-01-10.at.09.00.36.mov

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Co-authored-by: himanshupathak95 <abcd95@git.wordpress.org>
Co-authored-by: juanfra <juanfra@git.wordpress.org>

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