support sharing host fonts with toolbox

[juhp]

Is your feature request related to a problem? Please describe.

It would be cool to have a consistent way to use host fonts from within toolbox.

Describe the solution you'd like

I may be tricky to find a general consistent approach, though what I personally do
is for Fedora toolboxes (on Fedora):

sudo ln -s /run/host/usr/share/fonts /usr/local/share/

without running fc-cache.

Though apparently bad things can happen with this for Silverblue with fc-cache due to the timestamps.

FWIW, distrobox-init seems to do something like this:
https://github.com/89luca89/distrobox/blob/18053c254a83750c49c08e58df2e48a0f04aef48/distrobox-init#L2007