UPDATE 27/11/19: ConcernedApe has now released the full changelog detailing all the new content to hit Stardew Valley this week.
On top of all the changes mentioned in the article below, there are interesting new additions like new events, clothes tailoring and dyeing, hundreds of new items, and some all new areas to explore.
There's a new mineshaft dungeon right next to the quarry with new Haunted Skull and Sludge monsters, and if you reach the end of this dungeon you're rewarded with the new Golden Scythe. I accidentally found this dungeon playing last night and discovered these new enemies are pretty tough, though I also learned (from them killing me) there's a quality of life change when you "die" in Stardew, where it will show you a list of the items you've lost.
