Add Gatsby to list of topics

topics/gatsby/index.md

@@ -0,0 +1,13 @@
+---
+created_by: Ilesh Mistry
+display_name: Gatsby
+github_url: https://github.com/gatsbyjs/gatsby
+logo: gatsby.png
+related: React, open-source-framework
+released: 2015
+short_description: Gatsby is a free and open source framework based on React that helps developers build blazing fast websites and apps.
+topic: Gatsby
+url: https://www.gatsbyjs.org/
+---
+Gatsby is a free and open-source framework based on React that helps developers build blazing-fast websites and apps.
+It helps towards website development working with headless CMS's for modern tooling.