ESP8266 - WiFi Speedtest API

Hello! I am looking for a free WiFi Speedtest API that would print out the Mbps in the serial first as I then would implement it to display the values realtime in AJAX. But the problem is that I couldn't find an API that is either understandable or OOB working with ESP8266/Arduino.

I was looking at this API, but I do not understand how to implement it in my project.

branchard/fast-speedtest-api: fast.com API / CLI tool (github.com)

Can someone help me with it?