feat(wezterm): add <ctrl-bb> binding to go to the previous tab

When developing I often want to quickly swap between vim and a terminal. The
vim built in terminal does not really work for be. I prefer to use a proper
terminal.

Now you can quickly swap by pressing <LEADER-b> this is the same kind of
workflow I have in vim by using the <LEADER-TAB>

site-modules/core/files/wezterm.lua

@@ -128,5 +128,11 @@ return {
     { key = "7", mods = "LEADER", action = wezterm.action { ActivateTab = 6 } },
     { key = "8", mods = "LEADER", action = wezterm.action { ActivateTab = 7 } },
     { key = "9", mods = "LEADER", action = wezterm.action { ActivateTab = 8 } },
+
+    {
+      key = "b",
+      mods = "LEADER|CTRL",
+      action = wezterm.action.ActivateLastTab,
+    },
   },
 }