ENH: `volatility`: metric name should appear above plot as text

[nbokulich]

Improvement Description
The metric name shown on a volatility plot should appear as text, so that it can be copied/pasted (e.g., by a user who wants to then find that metric in a metadata file or metadata summary).

Current Behavior
The name appears above the plot, but as an image (?). Cannot be copied as text.

Proposed Behavior
Metric name should be copy-able. Either by printing as text or have a copy to clipboard widget.

References
forum xref