Document setting CSS variables for the Drawer component

[anastasialanz]

We can call out the CSS variables to change the height, width, top, and bottom styles, similar to the Table component docs.

• --drawer-width
• --drawer-height
• --drawer-bottom
• --drawer-top
• --drawer-animation-timing-function
• --drawer-animation-timing

[scurker]

We should include the new animation properties as well once from #1835