LSD uses Google Fonts

Hi GNUnet,

The LSD documents as published at https://lsd.gnunet.org currently use
Google Fonts. This is due to the default stylesheet used by the xml2rfc
tool.

I think there has been some recent discussion about the legality of
using Google Fonts in Europe. Besides that, I don't think it fits with
the spirit of the GNUnet project. I suggest not using Google Fonts.

One way of disabling usage of Google Fonts is to use a custom
stylesheet. The xml2rfc tool can be supplied a custom stylesheet with
the `-css` option. I have done this for the ERIS specification:

https://codeberg.org/eris/spec/commit/f62d7bc04ce89cc259f385b298a3d97c1ab32173

For LSD, this requires storing a custom stylesheet in every LSD repository.

Regards,
pukkamustard