Adding blog post link to readme (gatsbyjs#8397)

* Adding blog post link to readme

The current post referenced is for Gatsby Image V1. I've updated my post to V2 and added the blog link to the readme.

* Update README.md

packages/gatsby-image/README.md

@@ -127,7 +127,7 @@ export const query = graphql`
 `
 ```
 
-For another explanation of how to get started with gatsby-image, see this blog post by community member Kyle Gill [Image Optimization Made Easy with Gatsby.js](https://medium.com/@kyle.robert.gill/ridiculously-easy-image-optimization-with-gatsby-js-59d48e15db6e)
+For other explanations of how to get started with gatsby-image, see this blog post by community member Kyle Gill [Image Optimization Made Easy with Gatsby.js](https://medium.com/@kyle.robert.gill/ridiculously-easy-image-optimization-with-gatsby-js-59d48e15db6e) or this one by Hunter Chang (which also includes some details about changes to gatsby-image for Gatsby v2): [An Intro To Gatsby Image V2](https://codebushi.com/using-gatsby-image/)
 
 ## Two types of responsive images