Wrap the reader view article subtitle on narrow screens (#9369)
In the reader view, the feed name, authors and date share one
horizontal-list row whose items are `flex: 0 0 auto` and whose date is
a fixed 155px wide. The row could neither wrap nor shrink, so a long
feed name or author list pushed the date past the article box, and on
a phone the whole page scrolled sideways.
Let the row wrap and let its items shrink, so a long feed name is
ellipsized and the authors wrap inside the box. On narrow screens the
date then sits on its own line, so drop its fixed width there.
Rows that already fit are laid out as before.
Closes #9360
Abdelrhman Mohamed