Setup MobX Project from Scratch

[rwieruch]

Since it is a tedious task to upgrade all dependencies of an ejected create-react-app, maybe someone wants to help to set up this project with a fresh create-react-app version from scratch, ejecting it, installing MobX to it, and adding the implementation details of the App from before again.

See the-road-to-learn-react/react-mobx-local-state-example#1 for more information on this, whereas it is done in another project too.