Add v1.0.0 release blog post link to README

Author: raphael

README.md

@@ -8,6 +8,8 @@ goa is a framework for building microservices in Go using a unique design-first
 [![Godoc](https://godoc.org/github.com/goadesign/goa?status.svg)](http://godoc.org/github.com/goadesign/goa)
 [![Slack](https://img.shields.io/badge/slack-gophers-orange.svg?style=flat)](https://gophers.slack.com/messages/goa/)
 
+### v1.0.0 released! Read the [blog post](https://goa.design/blog/hello-goa/)
+
 ## Why goa?
 
 There are a number of good Go packages for writing modular web services out there so why build