chore(starters): add gatsby-gitbook-starter (gatsbyjs#14584)

docs/starters.yml

@@ -2878,3 +2878,20 @@
     - Comment feature (disqus, utterances)
     - Sponsor service (Buy-me-a-coffee)
     - CLI Tool
+- url: https://learn.hasura.io/graphql/react/introduction
+  repo: https://github.com/hasura/gatsby-gitbook-starter
+  description: A starter to generate docs/tutorial websites based on GitBook theme.
+  tags:
+    - Documentation
+    - MDX
+    - Markdown
+    - SEO
+  features:
+    - Write in Markdown / MDX and generate responsive documentation/tutorial web apps
+    - Fully Configurable
+    - Syntax highlighting with Prismjs
+    - Code diffing with +/-
+    - Google Analytics Integration
+    - SEO Tags with MDX frontmatter
+    - Edit on Github button
+    - Fully Customisable with rich embeds using React in MDX.