Create block theme: Google Fonts don't work

[adamziel]

As seen in #276, this won't work:

1. Install Create Block Theme on a WordPress Playground instance (example)
2. Go to Appearance -> Manage Theme Fonts -> Add Google font button
3. Select a Google font from the dropdown menu
4. Select a font variant from the list of fonts
5. Click the 'Add Google fonts to your theme' button
6. You should see the above error

Installing Google fonts involves network calls. Playground in the browser doesn't support that at the moment because of CORS and SSL problems – see #85. Can Google fonts feature be disabled for now?

cc @mikachan

[adamziel]

Solved by the fetch()-based network support added in #724