Change markup to be more valid

[illright]

We should add a block prop to the button to swap the underlying element for a <div>. Let that prop be incompatible with href.

We should also use <span> elements for Subhead and Label typographic components.

I'm thinking that Chip, Dot components should also become <span> instead of <div>.

Not sure what to do with Popover. Feels like it shouldn't affect the nature of its content. Maybe also a block prop? Feels weird