add REACT_APP_NAME to env sample

[ethanppl]

Some users log path in client\src\components\Settings\AppForm.tsx, becomes ~/.config/undefined/logs/main.log.

Code in client\src\components\Settings\AppForm.tsx:

constappName=process.env.REACT_APP_NAME;constplatform=(windowasany).platform;constlinuxPath=`~/.config/${appName}/logs/main.log`;constmacOSPath=`~/Library/Logs/${appName}/main.log`;constwindowsPath=`%USERPROFILE%\\AppData\\Roaming\${appName}\\logs\\main.log`;