navbar/toolbar uses flexbox

flex-box permits better layout on the navigation bar, akin to table
layout without the tags being in any particular order. Left is always
order 0, title/center is order 1, and right is order 2. The title will
expand to fill as much space as possible, but the left/right sides will
always get sufficient space to display their contents. While not
exactly native, it does mean one doesn’t have to worry about
positioning the title according to the other controls on the navigation
bar.