* 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

* fix #2223 - [feature] Implement dotenv-expand to accept variable expansion in dot env files

* add to README TOC

* fix readme

* Update README.md

* Better documentation for setupTests.js when ejecting

When running `npm run eject` before creating `src/setupTests.js`, the resulting `package.json` file, won't contain any entry for it - and this is correct in my opinion, since otherwise Jest will crash - but it's useful to have it documented and avoid pointless waste of time.

* Added additional note about src/setupTests.js

Added another note about src/setupTests.js and `npm run eject` in Testing Components section

* Update README.md

* Update README.md

'more' and 'simpler' together is incorrect.

* add support to set REACT_EDITOR to none

* change README message

* change condition to avoid problems with editor being null

* move condition to avoid extra code

* Update README.md with a note that reminds users to prepend REACT_APP_ to their environment variables. 
* Based on #865, where Dan Abramov suggests the person who filed the issue create a PR with these changes.
* Took the language from [Adding Custom Environment Variables](https://github.com/facebookincubator/create-react-app/tree/master/packages/react-scripts/template#adding-custom-environment-variables)

Replace `provide a lot value` with `provide a lot of value`.

* use safer/more aesthetic syntax

* fix typo

The launch configuration code provided is not compatible with VSCode since version 1.19.
The proposed documentation change is based on the response by a VSCode team member.

References:
https://github.com/facebookincubator/create-react-app/issues/3602#issuecomment-352075571
https://github.com/Microsoft/vscode/issues/40293#issuecomment-352017028

Replaced `it's` with `its`

the code got updated from `detect()` to `choosePort` while the comment did not.

Fix another dead link

* docs: adding section about debugging tests

* docs: removing node-inspector references

* docs: replacing terminal command with npm script

* Update README.md

* improve eject message

* cross os implementation

* extra watch options regex to react-dev-utils

* fix regex

* add test

* fix eslint error

* include react-dev-utils test in CI script

* attempt to fix import error

* attempt to fix error on CI

* Update .eslintrc

 - react-scripts@1.0.17