Adjust width of page nav buttons to avoid hiding the code block clip buttons

[noritada]

Since #894 was applied, it has been difficult to access the code clip buttons.
When I move the cursor from the lower left direction of the button, the next page navigation button covers the button before I reach it, as screenshots below shows.
(When I move the cursor from almost directly left of the button, I can reach it.)

This PR fixes that issue by reducing the width of the page navigation buttons.
I hope you will apply it if you like it.

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r? @ehuss

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[ehuss]

r? Kobzol

[Kobzol]

It seems like the navbar appears when the page width is >1080 pixels (https://github.com/rust-lang/mdBook/blob/05c6a9944696c470d62aa1b85e3613d9242755af/src/front-end/css/chrome.css#L194), and after my previous change we would ideally need to change this to something like ~1250 pixels.

Can you try adding this:

@media only screen and (max-width: 1250px) {
    .nav-wide-wrapper { display: none; }
    .nav-wrapper { display: none; }
}

to css/style.css, to see if it fixes the issue for you?

[apiraino]

I can reproduce the issue (or what I think the reported issue is about) if I enlarge the browser window just after the navigation buttons at the bottom turn into the "sidebar" navigation.

See this screencast

recording.mp4