[w3c/ServiceWorker] Update to reference HTML for link rel=serviceworker (#1073)

@sideshowbarker added formal definitions for link rel=serviceworker to HTML, containing e.g. authoring conformance requirements, in https://github.com/whatwg/html/pull/2356. The processing model of course stays in this spec. But there are some small tweaks that can be done for integration purposes.

- Update the introductory paragraph in https://w3c.github.io/ServiceWorker/#link-type-serviceworker. You still need to define the term "serviceworker link" but I'd say something like how it can be created with either a `Link` header or a HTML `<{link}>` element with `<{link/rel}>` equal to `"serviceworker"`. Ideally that last should link to https://html.spec.whatwg.org/multipage/semantics.html#link-type-serviceworker.
- https://w3c.github.io/ServiceWorker/#link-element-interface-extensions can be removed. That should hopefully make all links to the content attributes automatically go to their definitions in HTML.
- Step 7 should change to "Let workerType be the state of the `<{link/workertype}>` attribute". HTML now takes care of the missing and invalid value default.
  - Either step 8 should be removed (normative change!), or we should update HTML to have an invalid value default state (say "invalid"), which you can then throw an error on. Let me know what you think is best.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3c/ServiceWorker/issues/1073