Implement --limit-rate from curl

[jcamiel]

Implement --limit-rate from curl could be a good idea when you're testing a public API that have rate limiting.

Lib curl: https://curl.se/libcurl/c/CURLOPT_MAX_SEND_SPEED_LARGE.html

See curl manual --limit-rate

[danielbprice]

I'm doing some testing against a server which seems be behaving poorly for clients that are slow uploaders. This would really help me to simulate those conditions.

[danielbprice]

Thanks so much!