Move from xclock to own tiny implementation: zclock

Thanks xclock!

dotfiles/config/i3/config

 bindsym $mod+equal          exec "$spn pybmo menu gowork_focused"
 bindsym $mod+p              exec "$spn pybmo menu run"
 bindsym $mod+Shift+p        exec "$spn pybmo menu run_hist"
-bindsym $mod+o              exec "xclock"
+bindsym $mod+o              exec "zclock"
 bindsym $mod+d              exec "$spn pybmo menu ddg_hist"
 bindsym $mod+Shift+d        exec "$spn pybmo menu ddg"
 bindsym $mod+Shift+e        exec "$spn pybmo menu uemoji"