[2.x] Move the sidebar documentation to the documentation pages page

[caendesilva]

Targets #1818

This PR reorganizes and improves the documentation for navigation menus and documentation pages in Hyde. The main changes are:

1. Move sidebar-specific content from navigation.md to documentation-pages.md
2. Update customization.md to reflect the new organization
3. Add missing information about numerical prefix ordering to documentation-pages.md

Motivation:

• Reduce duplication and potential inconsistencies in the documentation
• Improve the overall organization of the docs, making it easier for users to find relevant information
• Ensure all features, including numerical prefix ordering, are properly documented

Benefits:

• Clearer separation of concerns between main navigation and documentation sidebar
• More comprehensive and accurate documentation for Hyde users
• Easier maintenance of documentation in the future

These changes will help Hyde users better understand and utilize the navigation and documentation features, leading to improved developer experience and more efficient use of the framework. Generally readers will be looking on how to use a specific feature such as main menus or sidebars, so it's distracting to have two areas in one file.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (89fe3e0) to head (8427e55).
Report is 1 commits behind head on unify-the-navigation-api.

Additional details and impacted files

@@                     Coverage Diff                      @@
##             unify-the-navigation-api     #1841   +/-   ##
============================================================
  Coverage                      100.00%   100.00%           
  Complexity                       1855      1855           
============================================================
  Files                             190       190           
  Lines                            4909      4909           
============================================================
  Hits                             4909      4909           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.