Add (or document?) a mechanism for a system wide install

[berolinux]

Hi, we're using Ungoogled Chromium as the main browser in our Linux distro (OpenMandriva), and would like to make extensions "just work" for the users. This project seems to be the right way to go about it - and works perfectly when installed as described in README.md. But there doesn't seem to be a way to automatically install it with ungoogled chromium for all users on the system -- every user seems to have to install the CRX through chromium's UI.

It would be nice to have a way to just have an unattended system wide installation of the plugin.