The ClassicTemplate is a class used to set up the Classic Template block on the server-side, and render the correct template.
From this file, we enqueue the front-end scripts necessary to enable dynamic functionality, such as the product gallery, add to basket etc.
From the render() method we inspect the $attributes object for a template property which helps determine which core PHP templating code to execute (e.g. single-product) for the front-end views.
