aiohttp module case-insensitive headers

[Tangerino]

Header field names are case-insensitive (RFC 9110 Sec. 5.1), so this code may break with some servers:

                if line.startswith(b"Transfer-Encoding:"):
                    if b"chunked" in line:
                        chunked = True
                elif line.startswith(b"Location:"):
                    url = line.rstrip().split(None, 1)[1].decode()