this plugin is only applied to gatsby v1. for v2 please use gatsby-mdx
yarn add gatsby-plugin-mdx
then
yarn add @mdx-js/mdx @mdx-js/loader loader-utils --dev
In your gatsby-config.js
plugins: ['gatsby-plugin-mdx'],
Check mdx document for syntax and examples: https://github.com/mdx-js/mdx#mdx-syntax
Check examples
folder for working examples