fix: Change defaults to match README

cb7dc21 improved the defaults for overseer, but omitted to set
actually set on_new_task to the value stated in the README.

lua/cmake-tools/const.lua

@@ -54,7 +54,11 @@ local const = {
             "terminal",
           },
         }, -- options to pass into the `overseer.new_task` command
-        on_new_task = function(task) end, -- a function that gets overseer.Task when it is created, before calling `task:start`
+        on_new_task = function(task)
+            require("overseer").open(
+                { enter = false, direction = "right" }
+            )
+        end, -- a function that gets overseer.Task when it is created, before calling `task:start`
       },
       terminal = {
         name = "Executor Terminal",