Describe the bug
A clear and concise description of what the bug is.

When viewing documentation pages, such as https://docs.python.org/3/reference/index.html, the navigation links (previous, next, index) are only present when the window is very wide. Navigation should always be available.
The left side nav bar can be shown with the hamburger menu, but there is no way to show page navigation with a narrow window.

To Reproduce
Steps to reproduce the behavior:
Using either Chrome or Firefox

1. Go to 'https://docs.python.org/3/reference/index.html'
2. Show window full width (see navigation)
   
3. Make window narrow enough to hide the left navigation pane.
4. Page navigation is gone, (along with breadcrumbs which is okay) and search box gets huge.
   

Expected behavior

The navigation should still be present when the window is narrow.
Reading documentation with a half screen window is common.
Reading in sequence using next is common.

Screenshots
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Additional context
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