Rate limit and custom User-Agent header

[abitsec]

Hi @xnl-h4ck3r,

Thanks for your great work. It would be useful to add the following two options to the tool, if possible:

• rate limit option specifying the maximum requests to send per second (in addition to the existing -p option)
• custom User-Agent header (it doesn't seem to be possible using the existing -u or -H options)

Kind regards, abitsec