Make Donut Example Responsive

[curran]

User story:

As a developer working on the responsive behavior of a component, I want to be able to test out both the horizontal and vertical resizing, so that I can implement the correct resize behavior.

Details:

While working on #441, I noticed that the Unovis Dev site does not allow you to test the responsive behavior of the donut chart. Horizontal resize works fine, but not vertical. I propose to modify the existing donut chart example to showcase vertical responsiveness.

Reproduction:

• npm run dev
• Navigate to http://localhost:9500/examples/Donut/Donut:%20Empty%20Segments
• Resize the browser horizontally - observe correct responsive layout
• Resize the browser vertically - observe that the container remains a fixed height

[curran]

Blocked by

• https://github.com/f5/unovis/issues/455