Customize Timestampedgeojson legend

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I have not see a way to customize the API somehow to be able to add a custom label or container that can hold a part of the date(e.g. Year) as the time-lapse is playing. The year will update from 2017 to 2018 as the visualization is playing.

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Being able to extract the year into its own container on the final time-lapse visualization.

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I did some research into the API and did not see a solution. I am not sure if there is an underlying solution using JavaScript from python.

Additional context

Implementation
folium is maintained by volunteers. Can you help make a PR if we want to implement this feature?

The issue names no files, tests, or entry points. Start by locating the TimestampedGeoJson implementation and its generated JavaScript, then determine how the time-lapse date is exposed to the visualization. Done means users can place the changing year in a separate custom legend container.