Adds a way to get the values of multiple Set-Cookie headers without combining them. In HTTP, Set-Cookie is a special header for historical reasons because it can appear multiple times in a response but cannot be combined, unlike other headers. Headers objects don't currently support having multiple values of the Set-Cookie header, and this feature adds that capability.
Docs: https://github.com/whatwg/fetch/issues/973#issuecomment-902578584 https://github.com/whatwg/fetch/issues/973#issuecomment-954815921