You can't, not easily at least. You used to be able to, but now Chrome addons need to have a valid signature from Google unless you have your users extract them

You can't, not easily at least. You used to be able to, but now Chrome addons need to have a valid signature from Google unless you have your users extract them, enable dev mode and install from the extracted directly and tolerate a warning that they're in dev mode every time their browser starts.