Added Go Reference Badge to Project README

README.md

@@ -4,6 +4,8 @@ A 2 dimensional Point.
 
 Get it `go get git.red-green.com/david/point2d`
 
+[![Go Reference](https://pkg.go.dev/badge/git.red-green.com/david/point2d.svg)](https://pkg.go.dev/git.red-green.com/david/point2d)
+
 ## Example
 
 ```go