Add material-ui/core flow-typed

[PolGuixe]

Add the library however some changes are required.

I need to open a discussion with the maintainers.

[PolGuixe]

I have opened an issue here flow-typed/flow-typed#2395

[PolGuixe]

Probably for the variables instead of just setting string types we should import the types from flow-typed to be used in our file eg:

import {Colors} from 'flow-typed/material-ui' // I don't think the import works this way

type Props = {
buttonColor: Colors
}