Collapsible Accordion

## 🚀 Feature Proposal

Customizable Component for collapse contents within an accordion.

## Motivation & Example

I want to provide a list of exercises, the user can select. But I want to keep it all on the same page, to let the user browse faster the items. The items should then be expandable and collapsible (different defaults each item, customizable content or icon for header and body).

See [bootstrap](https://getbootstrap.com/docs/4.3/components/collapse/#accordion-example).

Please correct me, if this feature is already implemented somehow.