adding the flat option to the readme

README.md

@@ -66,6 +66,7 @@ The `confetti` parameter is a single optional `options` object, which has the fo
 - `decay` _Number (default: 0.9)_: How quickly the confetti will lose speed. Keep this number between 0 and 1, otherwise the confetti will gain speed. Better yet, just never change it.
 - `gravity` _Number (default: 1)_: How quickly the particles are pulled down. 1 is full gravity, 0.5 is half gravity, etc., but there are no limits. You can even make particles go up if you'd like.
 - `drift` _Number (default: 0)_: How much to the side the confetti will drift. The default is 0, meaning that they will fall straight down. Use a negative number for left and positive number for right.
+- `flat` _Boolean (default: false)_: Optionally turns off the tilt and wobble that three dimensional confetti would have in the real world. Yeah, they look a little sad, but y'all asked for them, so don't blame me.
 - `ticks` _Number (default: 200)_: How many times the confetti will move. This is abstract... but play with it if the confetti disappear too quickly for you.
 - `origin` _Object_: Where to start firing confetti from. Feel free to launch off-screen if you'd like.
   - `origin.x` _Number (default: 0.5)_: The `x` position on the page, with `0` being the left edge and `1` being the right edge.