Allow passing a buff to LabeledDot

[nubDotDev]

Overview: What does this pull request change?

Previously, the radius of a LabeledDot was computed (if not provided) by adding 0.1 to half of the maximum of the label's width and height. Now we add a chosen buff to half the length of the (width, height) vector.

Motivation and Explanation: Why and how do your changes improve the library?

Links to added or changed documentation pages

Further Information and Comments

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested