draft(blog) 100DaysOfGatsby Challenge 12 (#22382)

* Draft challenge 12 article

* chore: format

* Fix typo

Co-authored-by: gatsbybot <mathews.kyle+gatsbybot@gmail.com>

docs/blog/100days/apps/index.md

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+---
+title: Challenge 12 - Transform Your Gatsby Website into a Web App
+date: 2020-03-18
+author: "Hashim Warren"
+excerpt: "Learn how to add dynamic features to your Gatsby site"
+tags: ["learning-to-code", "100-Days-of-Gatsby"]
+---
+
+_Gatsby was named the [#1 new technology to learn in 2020](https://www.cnbc.com/2019/12/02/10-hottest-tech-skills-that-could-pay-off-most-in-2020-says-new-report.html)!_
+
+_To help you learn about Gatsby and our ecosystem, we invite you to take the #100DaysOfGatsby challenge! If you are new to Gatsby, you can follow along with our beginner-friendly weekly prompts. Or if you are familiar with Gatsby and want to go deeper, we invite you to [build your first Gatsby Theme](/docs/themes/building-themes/)._
+
+_Learn more about [#100DaysOfGatsby here](/blog/100days)!_
+
+## Challenge 12: Add Gated Content to Your Website
+
+Did you know Gatsby can be used for websites as well as dynamic apps? Dustin Schau presented about this topic at Gatsby Days London:
+
+https://www.youtube.com/watch?v=zeVC-gD3u7M
+
+For example, if your project needs private routes, or sections of the site that only authenticated users can view, Gatsby can enable that with just a plugin, or by creating a few components from scratch. In the following resources we invite you to try both paths, and experiment with powerful third-party authentication services.
+
+### Gatsby for Apps Resources
+
+#### Overview & Examples
+
+First, get familiar with how [Gatsby works for apps](/docs/adding-app-and-website-functionality/).
+
+Then [watch this helpful livestream](/blog/2019-03-21-add-auth0-to-gatsby-livestream/) that covers adding an authentication service called Auth0 to your site.
+
+Lastly, play with live examples of these features by signing in to the [Gatsby Swag Store](https://store.gatsbyjs.org/), and [Gatsby Cloud](https://gatsbyjs.com/cloud)
+
+#### The Plugin Path
+
+To get started quickly, use `gatsby-plugin-create-client-paths` to create private client routes in your Gatsby site. [Learn more](/packages/gatsby-plugin-create-client-paths).
+
+#### The Hand-Rolled Path
+
+[Read this tutorial and handy illustration](/docs/client-only-routes-and-user-authentication/) that walks you through adding private routes and authentication in Gatsby.
+
+### What to Do If You Need Help
+
+If you get stuck during the challenge, you can ask for help from the [Gatsby community](/contributing/community/) and the [ASKGatsbyJS](https://twitter.com/AskGatsbyJS) Twitter account. You can find fellow Gatsby Developers on [Discord](https://discordapp.com/invite/gatsby), [Reddit](https://www.reddit.com/r/gatsbyjs/), [Spectrum](https://spectrum.chat/gatsby-js), and [Dev](https://dev.to/t/gatsby).