Guide for "Styled Components" missing some info so it breaks

[m2mathew]

Description

In the "Using CSS-in-JS library Styled Components" guide there is a step missing when adding the styled-components code to the pages/index.js file.

Based on the specific installation instruction provided, this component doesn't exist in the project at any point. It will break the app when running gatsby develop.

import Container from "../components/container";

Expected behavior

Show the user how to build the <Container> component so that that goodness of styled-components can shine through! 🌞

[calcsam]

Thanks for finding this! Want to add this?

[assimelha]

I can take this one if no one's working on it already :)

[KyleAMathews]

Fixed by @RxAssim in #3988 🎉