Add ability to chose where to download Roboto font files from

[Farenheid]

Hello, Privacy is becoming a great concern in UE, more and more people are reluctant to using Google services. Snap uses a "hardcoded" link to download Roboto fonts from Google servers. Every time a new version of Snap is released, I patch layout/header.php to make it download Roboto fonts from our own server. I would find it really handy if one could setup an alternate download URL from the theme parameters page in Moodle admin panel, so that no extra patching would be needed. Thanks a lot.