how to replace index.md with index.jsx

I pulled the [starter documentation demo](https://github.com/gatsbyjs/gatsby-starter-documentation), and added Semantic-UI to the project. How can I replace the default `index.md` file with a react component instead? I'm not sure why it's expecting index.md. I removed it.

```
.*$:33 Uncaught Error: Cannot find module './index.md'.
client.js:58 [HMR] connected
```
