When we have an approval flow, `pending-approval` will be the state a
broadcast is in between being a draft and broadcasting.
This means it is the earliest stage at which a broadcast can appear on
the dashboard, so this commit adds a new section at the top of the
dashboard to display these broadcasts (since the dashboard is in a
reverse chronological order).
Rather than displaying the scheduled time, the extra information shown
is the person who drafted the broadcast, since I reckon you’ll be coming
to this page because they’ve asked you to approve their broadcast.
The styling of the empty message seems to conflict with the hard-coded
widths added by the `dashboard-table` class. So we should only add the
`dashboard-table` class when there is content we need to control the
width of.
Same technique as we use for other pages that update via AJAX.
I’ve split the page up into separate chunks because the DiffDOM library
we use finds it easier to work out what’s changed when there are fewer
elements/a shallower tree.
