[BottomSheet] Add BottomSheet component

[oliviertassinari]

• PR has tests / docs demo, and is linted.
• Commit and PR titles begin with [ComponentName], and are in imperative form: "[Component] Fix leaky abstraction".
• Description explains the issue / use-case resolved, and auto-closes the related issue(s) (http://tr.im/vFqem).

Continuation of #4336.
I'm writing down some point raised by @nathanmarks that I want to address before merging this PR.

• usage of stage-1 for the documentation examples
• use RenderToLayer/Portal to escape the parent workflow.
• simplifying the layout computation
• optionally keep the elements in the DOM when closed
• open the SlidingSheet full screen.
• rebase this PR to the next branch.

Closes #2862.
Closes #2126.

[skirunman]

Great that a bottomsheet is being added as a component! I see this includes a refactor of the drawer component. Any thoughts on supporting google navigation drawers of type Permanent, Persistent and Mini variant that all push the content to the right? See #4752

[framerate]

I'm a big supporter of bottom sheet. Anything I can do to help with this PR?

[oliviertassinari]

@framerate I have paused the development of this new component as it was missing some key points (the check-list). That was some time ago.

Now, we should also migrate it to the next branch.
Any help is welcomed! I have other priorities as this moment. Feel free to continue this PR 👍.