After npm run deploy errors occured

After npm run deploy i have errors like above
Repo on Github

I am trying to deploy my react-app on gh-pages on Github (create-react-app)

'gh-pages' is not recognized as an internal or external command,
operable program or batch file.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! hello-world-4@0.1.0 deploy: `npm run build&&gh-pages -d build`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the hello-world-4@0.1.0 deploy script 'npm run build&&gh-page
s -d build'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the hello-world-4 package
,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     npm run build&&gh-pages -d build
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs hello-world-4
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls hello-world-4
npm ERR! There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\jan\AppData\Roaming\npm-cache\_logs\2017-05-12T17_55_00_56
9Z-debug.log

via Lukas