Support setting libcurl easy_setopt options for requests

[guzba]

See https://forum.nim-lang.org/t/10893#72823

[xjzh123]

I have made a fork of curly with such a function, but idk why I cant pass the test case and memory error occurs. Basic functionality is available. Maybe you can try it. https://github.com/xjzh123/curlyfork