Add Google Font(s) to Typography Customizer

@replace font-slug, font[name]:@str, font[variants]:@arr, font[category]:@str

// Add Google Fonts to the typography font options in the customizer
add_filter( 'generate_typography_customize_list', function ( $fonts ) {

   $fonts['monoton'] = array( 
      'name' => 'Monoton',
      'variants' => array( '400' ),
      'category' => 'cursive'
   );

   $fonts['fanwood_text'] = array(
      'name' => 'Fanwood Text',
      'variants' => array( '400', '400i' ),
      'category' => 'serif'
   );
	
   return $fonts;

} );

Source