Add theme support for responsive embeds.

Ensures that alignfull & alignwide embeds are scaled to take up the space they're given. (and that they are responsive 🙂)

functions.php

@@ -109,6 +109,9 @@ function gutenbergtheme_setup() {
 				'color' => '#444',
 			),
 		) );
+
+		// Add support for responsive embeds.
+		add_theme_support( 'responsive-embeds' );
 	}
 endif;
 add_action( 'after_setup_theme', 'gutenbergtheme_setup' );