Extend Documentation about EmptyState in Grid

[SebastianKuehnau]

Please extend the documentation (https://vaadin.com/docs/latest/components/grid#empty-state) about the EmptyState in the grid with a section and also a short demo that components can be added to the grid in an EmptyState. So both options are mentioned.

If you think this issue is important, add a 👍 reaction to help the community and maintainers prioritize this issue.

[rolfsmeds]

I think it would be overkill with two samples for this feature (one with a text and one with a component), especially seeing as how Grid samples are rather heavy, but perha, s it would be better to have a component sample instead of a text sample, or at least make it more clear in the text that you could use either.