File download option

- A file download feature should be added.
- The button can be added above the input box with the other buttons.
- A [Material UI download icon (SVG)](https://fonts.google.com/icons?selected=Material+Icons&icon.query=download) should be used for the image in the button.
- On clicking, the contents of the input box should be downloaded. **The user should be prompted to name their file.**

Review the UI entry point that renders the input box and its existing buttons. Add the download control with the specified Material UI icon, then verify that clicking it prompts for a filename and downloads the input contents.

Written by the indexing model from the issue text.