Update README.md

Author: ryanlintott

README.md

@@ -27,6 +27,7 @@ Features:
 - [`RelatableValue`](#relatablevalue), an enum used to store `.relative` or `.absolute` values.
 - [`SketchyLine`](#sketchyline), an animatable line `Shape` that aligns to frame edges and can extend beyond the frame.
 - [`.emboss()` or `.deboss()`](#emboss-or-deboss) any SwiftUI `Shape` or `View`.
+- [`AnimatablePack`](#animatablepack) as an alternative to `AnimatablePair` that takes any number of properties.
 
 
 # ShapeUpExample
@@ -311,3 +312,31 @@ Extensions for `InsettableShape` and `View` that create an embossed or debossed
 
 <img width="205" alt="image" src="https://user-images.githubusercontent.com/2143656/157765787-a8bcdee3-fec3-40f8-8414-1c66ca073db6.png">
 
+## AnimatablePack
+*\*iOS 17 or macOS 14 and up only*
+
+Animate lots of properties in a `Shape` using `AnimatablePack` instead of nesting `AnimatablePair` types
+
+Here is an example of animatableData using AnimatablePair:
+ ```swift
+ struct MyShape: Animatable {
+     var animatableData: AnimatablePair<CGFloat, AnimatablePair<RelatableValue, Double>> {
+         get { AnimatablePair(insetAmount, AnimatablePair(cornerRadius, rotation)) }
+         set {
+             insetAmount = newValue.first
+             cornerRadius = newValue.second.first
+             rotation = newValue.second.second
+         }
+     }
+ }
+ ```
+ You can see how it would get quite large once you start adding more than a few properties.
+ Here's how to use AnimatablePack instead:
+ ```swift
+ struct MyShape: Animatable {
+     var animatableData: AnimatablePack<CGFloat, RelatableValue, Double> {
+         get { AnimatablePack(insetAmount, cornerRadius, rotation) }
+         set { (insetAmount, cornerRadius, rotation) = newValue() }
+     }
+ }
+ ```