PXD-373 ⁃ try to move build to typescript or flow

[frickjack]

this will allow us to introduce static type checking into our code -

https://www.typescriptlang.org/docs/handbook/react-&-webpack.html https://flow.org/en/ https://discuss.reactjs.org/t/if-typescript-is-so-great-how-come-all-notable-reactjs-projects-use-babel/4887/3