Add a "When to use" section

[jjenzz]

There is sometimes visual overlap with our components which makes it a little unclear which pattern is the correct one to choose for a particular use-case. Most recently, we've had a request to make Tooltip appear on click on mobile with a reference to our info icon in the props tables as an example (which actually uses Popover).

It might be nice to provide some sort of tree diagram with questions and yes/no answers that direct folks down the right path.