[Component Request] Sheets (Bottom and Side)

[parlough]

These are both great components for web apps which support both desktop and mobile due to their flexibility. I don't currently have a use for a side sheet in my app, but a bottom sheet would be great for a few uses of mine.

Bottom: https://material.io/design/components/sheets-bottom.html Side: https://material.io/design/components/sheets-side.html

Thanks for your hard work and I appreciate the recent first class support for mdc-web's card!