Replace #26761
It's better to keep children elements simple, and let parent containers
layout the necessary padding/margin.
The old `not(:last-child)` and `.flex-item + .flex-item` are not easy to
maintain (for example, what if the developer would like to use a "tiny
height" item?)
The old approach also makes some UI look strange because the first item
doesn't have proper padding-top.
In this PR, we just simply use `.flex-item { padding: ... }`:
* Developers could manually set the item height they want easily
* It's easier to make it work with various containers -- with padding
(`ui segment`) and without padding (`div`)
And added more samples/examples.
Co-authored-by: Giteabot <teabot@gitea.io>
1a9998ce91