[Feature]: Custom, Collapsible Panels

[luketych]

What

The ability to collapse the "Description", "Acceptance Criteria", "Implementation Plan", "Implementation Notes" panels.
The ability to create and use custom panels in addition to the above.

Why

Makes it easier to view cards and get a simplified overview of everything before diving into the details.
Developer can add their own panels, or remove panels based on the unique needs of the project being worked on.