Chart popovers: Display description & link

Problem

• Currently, chart popovers only displays information from the Y-value of the chart
• Sometimes users are unfamiliar with certain metrics - they either want a brief description or to find out more in some documentation
• For some use cases, there is a need to highlight additional data that is relevant but not shown in the chart

Example use case with % increase	Popover structure

Proposal

• Allow chart popovers to optionally display description (and documentation link) below the metrics