* Add agenda widget with accordion
* Add AgendaItem, README, and do some cleanup
* Handle PR Feedback: Rename AgendaAccordion to AgendaGroup, accept an href prop for a non-accordion state. Accept onClick or href for AgendaItem, a11y fixes, fix some typos, update examples & README.
* Address PR Feedback: Rename AgendaGroup to AgenaHeader, use a direct link for href mode, use IconButton instead of Button & Dashicon, pull out link rendering to its own method. Use <Link /> for app links.
* Combine box-shadow focus/hover rule and add transparent background
* Make `count` optional
* Refactor dashboard layout into new Layout components
* Style the new layout
* Use Slot/Fill for the Header component
* Center cards, fixed size for sidebar
* Only set the box-sizing on things within our app
* Make app the full height of the wp-admin frame
* Add styles to show/hide sidebar
* Toggle the sidebar
* Wrap router around entire Layout, use page setting to show/hide sidebar on page
* Fix the styles on show/hide buttons, add title & close button to the sidebar
* Use a min-height on visible sidebars
* Add/update READMEs
* Update space between main content & sidebar
Justin Shreve
Kelly Dwan