This commit displays the date in addition to the time in the event read indicator's overlay drawer.

Type: add

BUG: https://iron.lily-is.land/T60

Verify that the overlay drawer in the event read indicator shows the date in addition to time.

Note that we do not add a unit test to MatrixEventReader::formattedTime because we cannot guarantee any particular format in the returned string, as it depends on the locale.