A simple page that embeds two tracking iframes that try to access storage and include buttons to interact with the Storage Access API.
NOTE: you must have `dom.storage_access.enabled = true`.
If your testing the tracking cookie restrictions feature, you should also have:
* `urlclassifier.trackingAnnotationTable.testEntries = storage-access.englehardt-tracker.com`
* `network.cookie.cookieBehavior = 4`
Access denied? Try interacting with the tracker first. Note that this link does not have an opener relationship, so it shouldn't lead to storage activation by heuristic.