Hi ! According to https://github.com/alexkuz/react-json-tree/issues/100, it is not possible to customize the [`JSONArrow` component](https://github.com/reduxjs/redux-devtools/blob/master/packages/react-json-tree/src/JSONArrow.js). I need to change this arrow by a `+/-` or another icon. Does PR are welcome or you don't want to offer this option ? Thanks a lot ! :)