Docs: write a step by step guide for newbies

[syncush]

As of today, Predator has "My first test" tutorial on its doc website.
There are 2 problems:

1. it is outdated (old screenshots, doesn't highlight new features)

2. the guide is not complete.

We would like to create a new guide which is very steps oriented, by that I mean that I would expect the guide to include something like this:

"copy that"
"put that here"
 "press run"
"go to reports" 
 "see your report"
"congratz, you just ran a load test on Predator🚀!"  
"Click here for the next guide on how to run a functional test"

@NivLipetz @enudler lets go down in detail on what exactly we would like to have.