Show current download upload speed on panel.
This extension is a Gnome 45 adaption of https://github.com/AlynxZhou/gnome-shell-extension-net-speed
Forked from https://github.com/pinguXpingu/pinguXnetLabel
It shows a text like ↓ 20.45 M/s ↑ 800.42 K/s on the right part of panel.
