Preserve num lock state when loading custom keymap

[mgabor3141]

Normally when you set a custom keymap, the numlock setting stops working. This patch fixes that.

Example config:

input {
    keyboard {
        xkb {
            // layout "us"
            file "~/.config/xkb/keymap.xkb"
        }
        numlock // Enable numlock on startup
    }
}