Improve item list ID and name when viewing a list of products

[martynmjones]

The value for item_list_id is currently set to engagement and item_list_name set to Viewing products when viewing a list of products.

That event could potentially be triggered from a number of areas on a website so we should look to make this more relevant to where the product is being viewed.

woocommerce-google-analytics-integration/assets/js/src/tracking.js

Line 23 in 813b7ee

item_list_id: 'engagement',

Originally reported in #311 (comment)