Revisit/update page reference docs

[cpsievert]

It feels like page references should gain more explanation and be reorganized as:

Dashboards

• page_sidebar()
• page_navbar()

Filled page

• page_fillable()

Basic pages

• page_fixed()
• page_fluid()
• page()

[gadenbuie]

Need to pull out page_fillable() and page_navar() from the page() docs.

[github-actions]

This issue has been automatically locked. If you have found a related problem, please open a new issue (with a reproducible example or feature request) and link to this issue.
🙋 Need help? Connect with us on Discord or Posit Community.