Hi!

I would like to know the possibility of creating a form of "global variable" to use in Gnome Shell CSS theme making to respect the user preferred font? I see this a lot in Qt development (mostly colors) but not in Gnome (and I'm not talking about SASS variables).

As an example, in gnome-shell my favourite theme is Arc, so I have in "stage" the following rule:

```
font-family: Futura Bk bt, Cantarell, Sans-Serif;
```

Well, I don't mind using Futura, but I do prefer to use my already chosen custom font for Gnome, which already resides at "/org/gnome/desktop/interface/font-name". So, for theme makers - even though they might prefer to use their fonts - I think the user configuration should be taken in concern. I'm not creative at giving ideas, specially for this situation, so my suggestion might look creepy, but it can give a better idea of what the CSS could look like (if any suggestion applies):

```
font-family: "@1", Futura Bk bt, Cantarell, Sans-Serif;
...
font-family: "${org.gnome.desktop.interface.font-name}", Futura Bk bt, Cantarell, Sans-Serif;
..
font-family: dconf('org.gnome.desktop.interface.font-name'), Futura Bk bt, Cantarell, Sans-Serif;

```

I'm filling this enhancement because I even have made a script to "automate" the task when the theme is updated, so my desktop looks uniform :)

My best regards,
Richard.