Added shebang to tell unix systems to use node

[NguyenDa18]

Received command not found error when running node-prototype-repl on ubuntu: https://stackoverflow.com/questions/34353512/node-npm-package-throw-use-strict-command-not-found-after-publish-and-install-g.

Adding the shebang tells "*nix systems that the interpreter of our JavaScript file should be /usr/bin/env node which looks up for the locally-installed node executable".

• https://medium.com/netscape/a-guide-to-create-a-nodejs-command-line-package-c2166ad0452e

[devsnek]

Thanks!