Definition of "here's"

“[…] the awfully hearty sort of Christmas cards that people do send to other people that they don't know at all well. You know. The kind that have mottoes like Here's rattling good luck and roaring good cheer, / With lashings of food and great hogsheads of beer. […]”

1922, Ben Travers, chapter 1, in A Cuckoo in the Nest‎