Adding a missing solution for an additional question

[avivmu]

In https://developer.mozilla.org/en-US/docs/Learn/CSS/CSS_layout/Grid_skills#Grid_Layout_Two there is an additional question:

Can you now cause the first item to display on top without changing the order of items in the source?

I thought it would be useful to add at least one acceptable solution.
I admit that my text might be improved, as I was focusing more on the solution itself.
@chrisdavidmills I mention you because otherwise no one will approve/deny this

[chrisdavidmills]

@avivmu thanks for providing a solution for this question. This is looking pretty good; I just had a few comments/suggestions:

1. Since the default order value is 0, you only need the first rule, and can remove the second one.
2. Maybe also show an alternative solution using z-index?
3. You need to put a space in between ### and Additional question for the markdown to render properly.

[avivmu]

Updated with your comments

[chrisdavidmills]

thanks!