Debugging: Leave a breadcrub when something is bound #503
Description
On really complex projects, it can become daunting to know exactly where an element's value is bound from - there may be many nested pages with dynamic paths, full of custom components. Where does one particular span get its textContent from?
When in debug mode, the Binder classes could leave a debug attribute on the element once it has been bound, indicating exactly where the binding was done from. e.g. <span data-bound-from="page/_component/my-thing.php:29">This is bound!</span>.
Whether we're in debug mode can be passed into the constructor, loaded from the config.ini.