No way to target container on first page load with skipInitialTransition set to true

[IWMTom]

When the skipInitialTransition prop is true, the div element created as a container does not have a class that can be used to target the element on first page load.

This is proving a problem in a project where I need to set html, body and #__next to height: 100%;

I also need to set it on to the container div so that I can use height: 100% in children, but without a way to target it specifically I cannot set the CSS appropriately.

With skipInitialTransition set to false this isn't an issue as the .page-transition-enter-done class exists at that point.

I propose a .page-transition-default class to be added to the container when the state passed to the buildClassName function does not match any of the specified cases, (i.e. the default case).

Thoughts?