Add Expandable Section Component

[interactivellama]

Simple hide/show. API should probably be similar to Accordion.

https://www.lightningdesignsystem.com/components/expandable-section/

[kyleheddon]

This is something my team has worked on for our internal project. Has there been any work done on this?

[interactivellama]

No, no one is currently working on it. I'm guessing it's simple enough that teams have been just making their own.

[interactivellama]

This is a list of relatively small in scope components that I put together base-component Simple components that are the building blocks of other components earlier this year.

[interactivellama]

@kyleheddon
@kevinparkerson is updating AppLauncher and will be creating an Expandable Section, since App Launcher has one inside of it anyway. If you have anything in the works, could you push it up in a WIP pull request? If not, that's cool, too.

[kyleheddon]

@interactivellama We do not have anything ready outside of our internal Pardot repo. It would probably simpler if @kevinparkerson implemented it