Add a CodeQL badge to the README

We added a CodeQL configuration in #202 but did not add a badge.

Author: mcdonnnj

README.md

@@ -1,6 +1,7 @@
 # skeleton-generic #
 
 [![GitHub Build Status](https://github.com/cisagov/skeleton-generic/workflows/build/badge.svg)](https://github.com/cisagov/skeleton-generic/actions)
+[![CodeQL](https://github.com/cisagov/skeleton-generic/workflows/CodeQL/badge.svg)](https://github.com/cisagov/skeleton-generic/actions/workflows/codeql-analysis.yml)
 
 This is a generic skeleton project that can be used to quickly get a
 new [cisagov](https://github.com/cisagov) GitHub project started.