CSS Shadow Parts, CSS Variables, Custom Events, and using Slot for scoping card logic

This lesson uses examples produced by students trying to produce a "card" as a web component. This covers CSS considerations and how to modify styles using variables and reflected attributes. Then it gets into using Slot to rescope a parent to child relationship for composability. Lastly, Custom Events and ensuring a 1 to 1 state management binding between an HTML element and our web component.