See facebook#3837

Update User Guide's README.md to include `json` and `css`
files in the command to format the entire project for the first time
with prettier, that it's consistent with the `lint-staged` command.

…in a $. (facebook#4000)

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This reverts commit bab2c29.

I meant to apply it to `next` instead.

 - create-react-app@1.5.2
 - react-scripts@1.1.1

Support for .mjs files added in facebook#3239 did not account for npm libraries which ship native mjs files alongside js files. This accounts for this by ensuring .js files resolve before their accompanying .mjs file. Note that this is not an ideal end state since selecting a .mjs over a .js extension should be the result of whether `import` was used instead of `require()` in a node environment with native ESM support (currently via `--experimental-modules`). Instead, this change just *always* selects a .js extension before the .mjs extension if it exists.

This unbreaks support for using GraphQL (relay, apollo, etc) within create-react-app projects.

Add troubleshooting for an issue that has to do with either 2FA, or using Windows, or both, when trying to deploy an app via gh-pages

This is just to correct the typo "Lets check" in a comment to "Let's check".