bug#51137: 29.0.50; Make documentation more readable in mobile devices

[Eli Zaretskii]

> From: Carlos Pita <carlosjosepita2@gmail.com>
> Date: Mon, 11 Oct 2021 16:06:37 -0300
> 
> In my phone the navigation links and the subsection links are barely
> visible and not proportionate to the body text, which is not only
> unpleasant to look at but, more importantly, makes it very difficult to
> navigate through the manual. See the attached screenshot.

Isn't it a problem with the fonts installed on the phone?