fix cookie with comma (#15319)

lib/pure/httpcore.nim

@@ -229,7 +229,11 @@ proc parseHeader*(line: string): tuple[key: string, value: seq[string]] =
   i = line.parseUntil(result.key, ':')
   inc(i) # skip :
   if i < len(line):
-    i += parseList(line, result.value, i)
+    if cmpIgnoreCase(result.key, "cookie") == 0:
+      i += line.skipWhitespace(i)
+      result.value.add line.substr(i)
+    else:
+      i += parseList(line, result.value, i)
   elif result.key.len > 0:
     result.value = @[""]
   else: