added functions palette screenshot (#8)

Author: jimkring

README.md

@@ -1,3 +1,13 @@
 # OpenG Array Library
 
+The OpenG Array Library package contains several routines for operating on array data.
+
+## Installation
+
 [Install the OpenG Array Library with VIPM](https://www.vipm.io/package/oglib_array/) (a.k.a. oglib\_array)
+
+## Overview
+
+### Functions Palette
+
+![Functions Palette](docs/functions_palette.png)