The getViewportDimentions on iOS returns wrong data

This [line](https://github.com/facebook/fbjs/blob/d308fa83c99c93e8e588de3396cf55b31e56b14e/packages/fbjs/src/core/dom/getViewportDimensions.js#L46) relies on `window.innerHeight`. This property is a [known troublemaker on iOS](https://benfrain.com/the-ios-safari-menu-bar-is-hostile-to-web-apps-discuss/).