Add docs for @vx/point. Issue airbnb#9

packages/vx-point/Readme.md

@@ -1,5 +1,27 @@
 # @vx/point
 
+A simple class to represent an x, y coordinate.
+
+## Example Usage
+
+```
+import Point from '@vx/point';
+
+let point  = new Point({x: 2, y: 3});
+let {x, y} = point.value()   // Get the cords from the point
+let array  = point.toArray() // Convert point to array
+```
+
+## Methods
+
+### `point.value()`
+
+Returns an `{x, y}` object with the x and y coordinates.
+
+### `point.toArray()`
+
+Returns the coordinates as an array `[x, y]`.
+
 ## vx packages
 
 - [@vx/axis](https://github.com/hshoff/vx/tree/master/packages/vx-axis)