Expand Toolbar when editor in Full Screen mode about bookstack

[ssddanbrown]

Thanks for the request @MartynKeigher.
I've been thinking about this while working on a new potential editor implementation #5058, specifically thinking about always expanding the sections to avoid overflow if there's space.
My initial target will be to match the existing editor 1:1 though until we get it stable, but I'll keep this open for the future.

If you're familiar with JavaScript, you could alter the existing editor toolbar via the public events we expose which provide access to the underlying config and libraries. There's an example of altering the toolbar somewhat at the top of this hack.