Incorporate breakpoints into preconnect links added by Embed Optimizer

[westonruter]

It would be slightly better if the viewport widths were also taken into account, so that an embed only visible on desktop would not get preconnected on mobile. This can be addressed in a follow-up PR.

Originally posted by @westonruter in #1302 (comment)

Code in question:

performance/plugins/embed-optimizer/class-embed-optimizer-tag-visitor.php

Lines 89 to 96 in 84bf4ee

	foreach ( $preconnect_hrefs as $preconnect_href ) {
	$this->link_collection->add_link(
	array(
	'rel' => 'preconnect',
	'href' => $preconnect_href,
	)
	);
	}