Fix bug: nvim_echo must not be called in a lua loop callback

Fixes #6

Fix the 'nvim_echo must not be called in a lua loop callback' error when a break ends.

* **lua/pomodoro/log.lua**
  - Use `vim.schedule` to call `vim.notify` in the `info` function.
  - Use `vim.schedule` to call `vim.notify` in the `error` function.

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For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/QuentinGruber/pomodoro.nvim/issues/6?shareId=XXXX-XXXX-XXXX-XXXX).

Author: QuentinGruber

lua/pomodoro/log.lua

@@ -3,10 +3,15 @@ local log = {}
 local p = "[pomodoro.nvim] "
 
 function log.info(txt)
-    vim.notify(p .. txt)
+    vim.schedule(function()
+        vim.notify(p .. txt)
+    end)
 end
 
 function log.error(txt)
-    vim.notify(p .. txt)
+    vim.schedule(function()
+        vim.notify(p .. txt)
+    end)
 end
+
 return log