Legend should allow copying contents to clipboard

As a user, when I hover over a graph to see the legend, sometimes I find very helpful data at a particular point. I would like to consume this useful data in other ways than only being able to look at it.

Copying the data in the legend would help with consuming and acting on this data (outside of interacting with the UI and Giraffe). Please create a way to efficiently allow the user to get the current contents of the legend into the clipboard.

Start by locating the TypeScript graph legend component and the hover-state rendering described in the issue. Check how the current legend contents are represented, then determine how clipboard access fits the existing UI behavior. Done means users can efficiently copy the legend contents for the hovered graph point.

Written by the indexing model from the issue text.