Add 'wait' option for server when using multi shots

[SamuelJennings]

I have a simple multi setup like this:

- server: python manage.py runserver
- output: home.png
  url: http://localhost:8000/

My problem is I have a rather large Django project and the server has not finished starting by the time the first shot is processed. So I end up with ERR_CONNECTION_REFUSED errors from playright.

I see in the code that there is a time.sleep(1) call, presumably to wait for the server to start?

My question is could we make this a customizable parameter? Maybe something as simple as:

- server: python manage.py runserver
  wait: 5

and then use the wait parameter in time.sleep.