[Gatsby] Add Doc

Author: agunggapai

README.md

@@ -5,6 +5,7 @@ Docker Implementation
 * React
   * [React](https://github.com/agung-learns/docker-implementation/tree/main/react/react-docker)
   * [NextJS](https://github.com/agung-learns/docker-implementation/tree/main/react/nextjs-docker)
+  * [Gatsby](https://github.com/agung-learns/docker-implementation/tree/main/react/gatsby-docker)
 * Vue
   * [NuxtJS](https://github.com/agung-learns/docker-implementation/tree/main/vue/nuxtjs-docker)
 * Angular