Update 'space between' functionality

[rmschindler]

As per https://tailwindcss.com/docs/space, space-x- and space-y- should inform margins, not padding.

[thheller]

Hmm weird. Could have sworn I got these from the tailwind website? Did they change them?

[rmschindler]

Actually scratch this pull request, because it is incomplete: I see here that there is more to the story: the combinator Tailwind uses is not the adjacent sibling (+) but the general sibling combinator (~). But though this is in the code, it is not reflected in the docs. So... I am confused as to what the rule should be.

As far as whether Tailwind changed their rules, I haven’t been able to find out yet.