badge for docs

Author: gigapod

README.md

@@ -4,6 +4,7 @@
 ![GitHub issues](https://img.shields.io/github/issues/sparkfun/SparkFun_Toolkit)
 ![GitHub release (with filter)](https://img.shields.io/github/v/release/sparkfun/SparkFun_Toolkit)
 ![GitHub (Pre-)Release Date](https://img.shields.io/github/release-date-pre/sparkfun/SparkFun_Toolkit)
+![Documentation Build](https://github.com/sparkfun/SparkFun_Toolkit/actions/workflows/build-deploy-ghpages.yml/badge.svg)
 
 The SparkFun Toolkit provides a common set of core functionality for use across the SparkFun Arduino Driver library. Instead of each device driver library implementing it's own communication layers, error types and design, the SparkFun Toolkit library is used.