Add "full-screen" modal type

[bashmish]

I'd like to have a modal which will take the full width and height of the plugin.

Right now I'm solving this with position="left" and some extra styles:

<Modal position="left" noTransition={true}>
  <div
    style={{
      width: '100vw',
      height: 'calc(100vh - 41px)',
      overflowY: 'auto',
    }}
  >
    {/* content goes here */}
  </div>
</Modal>

41px is the height of the modal top bar (magical, since I didn't find a CSS var for it).

I think it's much better to have such modal type out-of-the-box and not use magical number.
position="left" also breaks transition for me, because I want the center transition, not left, but center has border-radius on the modal which I can't remove on my side.