Enabling global styles to handle custom font declarations

[jffng]

To use a custom font, a theme today must do the following:

1. Enqueue it
2. Make a @font-face declaration in the theme’s stylesheet

As the current global styles mechanism is described, I think the steps would be:

1. Enqueue it
2. Make a @font-face declaration in the theme’s stylesheet
3. Add the font to theme.json in presets and styles, something like:
   { global: { presets: { fonts: [ "my font", "other font", ... ] } } }

Is it possible that theme.json processes font declarations, making at least step 2 unnecessary? I think this moves slightly beyond generating a CSS custom property.

cc @carolinan

[oandregal]

I've linked this issue from the tracking one. Font family is one of style attributes we'd like to add but haven't gotten there yet. Ideally, I'd like to see if the block style system can manage this for the theme.

[jffng]

Closing this issue as theme.json should not enqueue any fonts, and the font family mechanism has been added.