[docs] New images for spacers on several pages

[markcaron]

Create screenshots of the RH spacer tokens for the following elements' docs

• Elements/Cards
• Elements/Jump Links
• Elements/Popover
• Elements/Progress Steps

Also the Foundations/Spacing page likely needs some newer style images as well.

Originally posted by @markcaron in #1248 (comment)

[coreyvickery]

@markcaron I think we should move this to Diglett. The designers are planning several design and content audits as soon as the new year starts.

[bennypowers]

When you get to this, please use tshirt sizes in the legends instead of numbers - so we can subtly inculcate the "names, not values" aspect of tokens