Documentation for `.sydtest.yaml`

[GoPavel]

Hello! I was looking for a way to pass some arguments (--no-randomize-execution-order) automatically without writing a bash script or
Makefile. Thus, I have ended up with adding the parameter into .sydtest.yaml:

randomize-execution-order: false

Probably it will be useful to mention this feature somewhere unless it's not part of the public API. For example HSpec mentions this about .hspec file here: https://hspec.github.io/options.html

[NorfairKing]

Sure! PR welcome :)