Release testing instructions: Storefront 3.4.0

Fix escape function in comments template #1587

1. Go to Settings > Discussion and set the option Break comments into pages with to 5.
2. Add 6 comments to a post.
3. Verify the aria-label of #comment-nav-below has text.

Fix missing icons #1588

This PR fixes multiple bugs:

• Bug #1586 First test:

1. Verify stars in rated products are correctly displayed in PHP-based grid blocks (ie: Products by Category), All Products block and Review blocks.

• Bug #1586 Second test:

1. Force WC to show an error, you can do that in the Checkout block submitting the form with an empty address.
2. Verify the icon in the notice is displayed.

• Bug #1519

1. Rename your /wp-content/plugins/ folder to /wp-content/modules/.
2. Add these lines to wp-config.php:

define( 'WP_PLUGIN_DIR', dirname(__FILE__) . '/wp-content/modules' );
define( 'WP_PLUGIN_URL', 'https://{yoursite.com}/wp-content/modules' );

3. Verify icons are displayed across the store.