Add possibility to keep skin-wide spacing within grids

[woobione]

Case
When working with grids in PAM it's assumed that "end-user" will implement padding within the items in the grid. This might in the long term create inconsistencies in grid spacing and overall layout.

Suggestion
Add a general way to implement basic styling for grids with consistent grid spacing. If a user wants a more specific use case - let them build that. But the basics should be there.

Requirements

• Grids should have an option for spacing
• Optimally end-user can select to only space in y and/or x axis
• Add themability to grid spacing size
• Spacing should not change box model behavior
• Items within grid should not create outwards padding. Only pad between each other

[ollhar]

Nice suggestion. Let's implement it. We should also add a note to keep an eye on the draft suggestion for row-gap support for flexbox layouts, at the moment it has limited support for flexbox but well supported for grid layout.
Link: row-gap MDN