[Feature] Add an optional extension that can monitor script requests / loads and report

As outlined in #1539, suggest the creation of a new extension that can report the loaded scripts.

As suggested by @thoo1

For now I've accomplished listening to timing/size info for script loads using PerformanceObserver api, which like you said, isn't generally available to all browsers

Like you said, seems like getting the status of the script load isn't expose in the performance timing apis - it is only on the load/error event handlers