Http client headers updates

[hamishwillee]

A bit more tidying of HTTP client hint header reference pages in preparation for adding new headers discussed in:

• Incomplete information for Accept-CH page #1408
• Client hints updates #4907 (comment) and Client hints updates #4907 (comment)

Most of this is boilerplate addition to match our standard templates, and using the {{Specifications}} macro where defined. I did also create a page for the Width header and populate it with the information from the parent headers page. Doesn't add "much" more than that.

@Elchi3 You asked about specs. A lot of this stuff seems to have been implemented in Chrome without much of a spec. Anyway,

• This is chrome implementation info: https://chromestatus.com/feature/5642300464037888
• It seems likely nothing much has been done on FF but there is "interest" due to the new client UA hints: https://bugzilla.mozilla.org/show_bug.cgi?id=935216
• Given that they are at least mentioned, I think we could include these as "somewhat official": https://wicg.github.io/client-hints-infrastructure/#client-hints-token-definition : Save-Data, DPR, Width, Viewport-Width, Viewport-Height, Device-Memory, RTT, Downlink, ECT, Sec-CH-UA, Sec-CH-UA-Arch, Sec-CH-UA-Bitness, Sec-CH-UA-Full-Version, Sec-CH-UA-Mobile, Sec-CH-UA-Model, Sec-CH-UA-Platform, or Sec-CH-UA-Platform-Version,

[github-actions]

Preview URLs

• https://pr5784.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Headers/DPR
• https://pr5784.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Headers/Device-Memory
• https://pr5784.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Headers/Save-Data
• https://pr5784.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Headers/Width
• https://pr5784.content.dev.mdn.mozit.cloud/en-US/docs/MDN/Structures/Page_types/HTTP_header_page_template

Flaws

Note! 4 documents with no flaws that don't need to be listed. 🎉

URL: /en-US/docs/MDN/Structures/Page_types/HTTP_header_page_template
Title: HTTP header page template
on GitHub
Flaw count: 1

• bad_bcd_queries:
  • No BCD data for query: path.to.feature.NameOfTheHeader

External URLs

URL: /en-US/docs/Web/HTTP/Headers/DPR
Title: DPR
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/HTTP/Headers/Device-Memory
Title: Device-Memory
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/HTTP/Headers/Save-Data
Title: Save-Data
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/HTTP/Headers/Width
Title: Width
on GitHub

• https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/client-hints (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/MDN/Structures/Page_types/HTTP_header_page_template
Title: HTTP header page template
on GitHub

No new external URLs