Improves ergonomics for creating JSON Response objects. The Response constructor allows for creating the body of the response from many types, however it is not possible to directly create a JSON object. The Response.json() static method fills this gap. It returns a Response object with a body consisting the first argument serialized as JSON. The second argument is a ResponseInit option bag as with the Response constructor.
Creating a Response object with a body of a JSON object has been harder than the other types supported by Fetch. This change improves the ergonomics of creating a JSON response.
Explainers: https://docs.google.com/document/d/1dTycWmyxLZNGTBW93fvtf1IQahx-vNwgu94yT1x9K50/edit