Shortcut to move to last used tag

[Stefan Horomnea]

Hi,

I'm wondering what should I write in my rc.lua to assign a key shortcut
that moves me from current to the last used tag. The reason for this, is
that I often switch between two tags (say Alt + 2 and Alt + 8)..but after a
while I switch between Alt + 4 and Alt + 8, and it's simpler to have
something like Alt+Ctrl+L that switches between the latest two tags.

Thank you,
Stefan