Documentation: Hybrid navigation

[ecomodeller]

Hybrid navigation uses a context aware sidebar.

E.g. navigating to somewhere in the user guide: /user-guide/*

or on the api pages: /api/*

AI-generated summary

This pull request includes updates to the docs/_quarto.yml file to reorganize the sidebar navigation structure. The changes aim to improve the user experience by making the navigation more intuitive and structured.

Key changes include:

• Added a new "User Guide" section with links to relevant documentation files.
• Reorganized the "Examples" section to include sub-sections for different example types, making it easier to find specific examples.
• Introduced a new "API Reference" section with links to various API documentation files.
• Removed the old sidebar configuration and replaced it with a more structured and categorized format. [1] [2]