fix: update to new course outline structure and design

[rpenido]

Description

This PR updates the plugin structure to the new sidebar design.

For now, it only works for the Course Outline page.

Additional Information

• Related to: Course Outline: Course/Section/Subsection In Context Sidebar frontend-app-authoring#2639

Testing Instructions

• Check feat: create context for sidebarPages frontend-app-authoring#2827

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Private ref: FAL-4299

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[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.87%. Comparing base (595747f) to head (3015cac).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/index.ts	0.00%	1 Missing ⚠️
src/plugin-slots.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #115      +/-   ##
==========================================
+ Coverage   53.25%   57.87%   +4.62%     
==========================================
  Files          15       13       -2     
  Lines         338      311      -27     
  Branches       62       62              
==========================================
  Hits          180      180              
+ Misses        157      122      -35     
- Partials        1        9       +8     

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