First page of electron docs does not show code for all files in the given example

# Documentation style bug

The first page of the **electron** docs has a section titled **[Running examples with Electron Fiddle​](https://devdocs.io/electron/#running-examples-with-electron-fiddle)**. The documentation on the **[official site](https://www.electronjs.org/docs/latest/#running-examples-with-electron-fiddle)** for the same section has 3 files `main.js`, `preload.js` and `index.html`. However, devdocs shows the code for only `main.js`. There is no way to view the code for the other two files on devdocs.

Compare the Electron Fiddle section in the devdocs page with the corresponding section on the official Electron site. Start by tracing how that documentation page is sourced and rendered; done means the example exposes code for main.js, preload.js, and index.html, matching the official documentation.

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