Issue description

Running the virtualbox image for NixOS 18.09, hit this usability issue.

Steps to reproduce

1. Download the .ova file from
   https://releases.nixos.org/nixos/18.09/nixos-18.09beta78.6f3bd5db2f4/nixos-18.09beta78.6f3bd5db2f4-x86_64-linux.ova
2. Start it up in VirtualBox.
3. Once logged in, click on the KDE menu.
4. Click "Applications" -> "System" -> "View NixOS documentation in a web browser".

KDE asks what to use to open the .html file. No real option is available, you will have to install it yourself.

Possible solution

It would make sense to include a simple browser for graphical users. Alternatively, package documentation as a PDF and include a PDF reader.