add run scripts

[BlackYuzia]

Scripts

• start - runtime in default mode
• steam - runtime in steamworks mode

should also be added in to readme:

# npm run start
$ npm start      # default run
$ npm run steam  # steamwokrs run
$ npm run demo   # run force.js for check demo

You can run npm run demo or with arguments npm run demo -- demofile.dem 76561198843330785 "output.json"