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

Support for .mjs files added in #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.

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

This reverts commit bab2c295.

I meant to apply it to `next` instead.

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.

See #3837

 - babel-preset-react-app@3.1.1
 - create-react-app@1.5.0
 - eslint-config-react-app@2.1.0
 - react-dev-utils@5.0.0
 - react-error-overlay@4.0.0
 - react-scripts@1.1.0

* Test Node 9 on CI

* Oops

* Add warning when HOST environment variable is set (#3719)

* Improve HOST environment variable warning message

* Adjust text and message

Closes #3719

* Always include destructuring transform

* Fix lint

* Bump detect-port-alt

* Bump again

All FB open source projects including this one enforce [our code of conduct](https://code.facebook.com/pages/876921332402685/open-source-code-of-conduct), but I just realized we haven't explicitly linked to it from a Markdown file. So I'm doing just that.

* This is a good default.
Adds approx 4 seconds to install time, but can save some headaches.

* Add no lockfile for add, too

* Switch to Yarn Workspaces

* Feedback

* Move flowconfig

* Use publish script

* Keep git status check

* Fix Flow without perf penalty

* Remove Flow from package.json "test"

* Try running it from script directly (?)

* Try magic incantations

* lol flow COME ON

* Try to skip Flow on AppVeyor

* -df

* -df

* -df

* Try to fix CI

* Revert unrelated changes

* Update CONTRIBUTING.md

It's been here long enough.

* This doesn't look needed anymore

* Remove unnecessary rebuilds

* Convert e2e-installs

* Convert kitchensink tests

* Upgrade npm for kitchensink

* Run e2e-simple in a realistic scenario

* Use npx for everything

* oops

* Separate old Node E2E test

* Try this for old node

* Try to use Yarn in more E2E scripts

* Keep using npm pack

* Maybe this will fix Windows?

* Try this

* Use latest npm in e2e tests

* Keep default npm version in "simple" test

* Try to fix CI by using a version that supports Yarn

* add link to deployment docs after build

* Update printHostingInstructions.js