Series.Bubble - Using the Data Labels Element
A "data label" is text shown next to each data point that shows
its value. When the Data Labels element is used as a child of
Series.Bubble, text representing the data values can be configured to appear
on the chart, either inside or outside the bubbles:
The Data Labels element has attributes that allow you to control the font family, color, size, and weight, the data format, border color, and positioning of the text. The Data Labels element's color-related attribute values can be set using @Chart tokens.