Add [type] support to <ol> breadcrumbs.

[geoffrey-eisenbarth]

Allow users to opt in to numbers in <ol> breadcrumbs via the [type] attribute.

[geoffrey-eisenbarth]

I also added support for [aria-current=step], since I was drafting this up in the context of a checkout flow.

What do you think about replacing the separator / with e.g. > or → when the breadcrumbs contains [aria-current=step]?

Edit: perhaps in the spirit of issue #58, we can specify it with --breadcrumb-separator?

[geoffrey-eisenbarth]

Another thought: we could replace the :is(ul, ol)[role=list] styling with :is(ul, ol)[type=none] (e.g., set padding-inline-start:0).

Two possibly inconsequential asides:

• Lighthouse balks at <ul role=list> without explicit role=listitem children 🙄
• MDN says ul[type] is depreciated :(