SPIKE: auro-drawer: scoped scrolling

[braven112]

Is your feature request related to a problem? Please describe.

When a drawer needs to scroll we can have a situation where there are two scroll bars side by side. When the drawer is open though a user really only wants to scroll the drawer content, not the entire page.

Describe the solution you'd like

We can fix this by adding overflow: hidden to the body when a drawer is in an open state and then remove that line when the drawer is closed. We can likely do something similar in auro-dialog

Describe alternatives you've considered

Hide a scroll bar with css but that isn't well supported accross browsers.

Additional context

This is related to the fix we did on #17

[Patrick-Daly-AA]

Questions to answer with this SPIKE:

1. What is a real world scenario where the page being a drawer (or dialog) would want to be scrolled?
2. In what cases do we expect the scroll bar to appear?
3. Determine if we want to do this in Dialog or Drawer (IE, the two scroll bars right next to each other case)