Created by: iansu
Fast Refresh will now be enabled by default unless FAST_REFRESH=false is set.
The warning currently appears during compilation when starting the dev server. Once compilation is complete the console is cleared along with the warning. If we want the warning to be present at all times we can move it into react-dev-utils. However, it's harder to determine if the FAST_REFRESH environment variable is set at that point so we would have to show the warning always, even if the user has set FAST_REFRESH=false.