Add missing api.PushSubscriptionChangeEvent.PushSubscriptionChangeEvent feature (#18283)
Add missing api.PushSubscriptionChangeEvent.PushSubscriptionChangeEvent feature (#18283)

This PR is a part of a project to add missing interfaces and interface features to BCD that are from an active spec (including WICG specs) and is supported in at least one browser.  This particular PR adds the missing `PushSubscriptionChangeEvent` member of the PushSubscriptionChangeEvent API, populating the results using data from the [mdn-bcd-collector](https://mdn-bcd-collector.gooborg.com) project (v7.0.0).

Tests Used: https://mdn-bcd-collector.gooborg.com/tests/api/PushSubscriptionChangeEvent/PushSubscriptionChangeEvent
mdn/browser-compat-data,mdn/browser-compat-data