Add bubble maps support

[mwjames]

Is it possible to display size attributed bubbles [0] within maps created from property information as provided in/by #ask queries?

Use cases:

• City population by size
• Infected population (e.g. COVID-19) by size, age, gender etc.
• Car sales by country
• etc.

Example

[0] https://www.d3-graph-gallery.com/bubblemap

[JeroenDeDauw]

Maps does currently not support bubble maps at all. Would be a great feature though!