feat(http): add an option mark to set SO_MARK

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

http/client.lua

@@ -358,7 +358,10 @@ function methods:request(method, url, body, opts)
         headers[k:lower()] = v
     end
 
-    local answers, err = dns.query(host, { type = opts.ipv6 and dns.TYPE_AAAA or dns.TYPE_A })
+    local answers, err = dns.query(host, {
+        type = opts.ipv6 and dns.TYPE_AAAA or dns.TYPE_A,
+        mark = opts.mark
+    })
     if not answers then
         return nil, 'resolve "' .. host .. '" fail: ' .. err
     end
@@ -426,6 +429,7 @@ end
         insecure: A boolean, SSL connecting with insecure.
         ipv6: A boolean, parse ipv6 address for host.
         body_to_file: A string indicates that the body is to be written to the file.
+        mark: a number used to set SO_MARK to socket
 
     In case of failure, the function returns nil followed by an error message.
     If successful, returns a table contains the