Service Worker API - Blurb

[ashleymichal]

In addition to the pages about FetchEvent and CacheAPI, include a short blurb about our implementation of the Service Worker API; previous versions of our documentation simply said we implemented "as much as makes sense", which is only intuitive if you are already familiar with the product. This piece should indicate something about the lifecycle (or lack thereof) of our Service Worker implementation -- scripts are pushed to the edge, rather than downloaded like they are in the browser, so installation and activation steps are unnecessary; additionally, all implementation tied to the attempt to sync up the versions of all instances of service workers, as is done in the browser, is impractical for our 6000+ machine network, and therefore we don't attempt, meaning that more than one version of your script may be active at a time across our network.

[ashleymichal]

this will just serve to confuse users. we will instead focus on a "lifetime of a request" #160 article for post-launch.