gtkmm-2.4 Offline documentation

[Siavash Safi <siavash safi gmail com>]

Hi,

The offline documentation of gtkmm-2.4 doesn't include the icons
directory and style.css file. it's very ugly and hard to read(my eyes
become tierd) without them. I downloaded and added them myself and it
works. It's better if you add them to the package on the website.

Regards,
Siavash Safi