(Feature request) Arbitrary subheading on lists

It would be pretty handy to be able to define part of a card's heading to be rendered as a subheading on a new line at the top of a list.

For instance, a subheading on a "Week X" list might contain the broad focus for the week, giving context to the cards contained within.

I'd also like to use this to highlight imminent deadlines, etc.

Thoughts?
