Request: referrerPolicy property
  The referrerPolicy read-only property of the
  Request interface returns the referrer policy, which governs what
  referrer information, sent in the Referer header, should be included
  with the request.
Value
  A string representing the request's referrerPolicy. For
  more information and possible values, see the Referrer-Policy HTTP
  header page.
Examples
  In the following snippet, we create a new request using the
  Request() constructor (for an image file in the same directory as
  the script), then save the request referrer policy in a variable:
js
const myRequest = new Request("flowers.jpg");
const myReferrer = myRequest.referrerPolicy; // returns "" by default
Specifications
| Specification | 
|---|
| Fetch Standard # ref-for-dom-request-referrerpolicy② | 
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