Yeah man, seriously you didn't know? Storyline else was surprised by this too. It's been there for the last five months or something!
In the editor at the bottom of you are in markdown it has an option to select files for upload or you can just drag and drop them from a folder on your PC!!
Holy crap!! Wot the feck!! Cor blimey!! Am I this blind!? I saw it only now!! Crap!! HAHAHA!!! I uploaded images the hard way for the entire length of A Day in the Clouds!!! hahahaha!
From now on in you will be laughing with joy and adding images left right and centre!!