and make opt-in for non-app clients
There's a tricky initialization balancing act happening here -- but
if we try to load the default style on a system missing the fonts
referenced in that style, then we risk trying to download those
fonts before the QgsNetworkAccessManager is ready.
So play it safe and defer all font download handling until the
QGIS app is fully launched.
available for use in QGIS
Allows for use of fonts which aren't installed system-wide in QGIS, e.g.
when the user does not have permission to install fonts on a system.
