show free HDD space as icon in top panel

[ferdymercury]

For monitoring the available HDD disk space, I always need to open an external application, I do not have an immediate visualizer in the top menu. This issue has been commented and solved in community forums for many years, but has never been implemented into the default monitor Ubuntu Gnome and MATE applets.

It would be nice to add one of these solutions into the default monitor menu icons of this repo, see below:
https://askubuntu.com/questions/829707/file-system-usage-indicator
paradoxxxzero/gnome-shell-system-monitor-applet#555