Merge pull request #144 from thewtex/github-action-badge

DOC: Add GitHub Actions Build badge

Author: thewtex

README.md

@@ -1,6 +1,8 @@
 ITK Software Guide
 ==================
 
+![Build](https://github.com/InsightSoftwareConsortium/ITKSoftwareGuide/workflows/Build/badge.svg)
+
 This [ITK Software Guide] is the handbook for developing software with ITK.
 
 It is divided into two companion books.