ipywidgets file chooser

There is no file chooser widget included by default in ipywidgets. There is a version implement in the [ipyfilechooser](https://pypi.org/project/ipyfilechooser/) package that we recommend using.

Alternatively, it should also be possible to implement this as a HTML download request that uses the standard browser mechanism to save a file.

No repository file, test, or entry point is identified in the issue. Start by reviewing the project structure and its use of ipywidgets, then compare the recommended ipyfilechooser package with the HTML download alternative. Done means selecting an implementation path and adding the requested file chooser widget.

Written by the indexing model from the issue text.