improve :download: role clarity

[julian-poidevin]

Hello and thanks for this really nice theme !

I wonder if the the Sphinx :download: role could be improved ?

When using the furo theme, the download link looks like this : https://sphinx-themes.org/sample-sites/sphinx-rtd-theme/kitchen-sink/generic/#download-links

Whereas, when using sphinx_rtd_theme, there is a more distinctive "download" button : https://sphinx-themes.org/sample-sites/sphinx-rtd-theme/kitchen-sink/generic/#download-links

I know one of furo rule is to be "Intentionally minimal" but I feel adding a minimal download icon, would help the documentation reader to figure out the link is not a "normal" link but a "download" link.