feat: native desktop notifications (experimental) (#59)

* desktop notification by entering `Mode::DONE` for `countdown` and `pomodoro`

* remove redundant `on_done_called` check

* remove build warning (release only)

* log notification errors

* cli arg to enable desktop notifications

* persistant notification settings

* ctrl shortcut

* update changelog

* max timer notification

src/storage.rs

@@ -1,5 +1,5 @@
 use crate::{
-    common::{AppTimeFormat, Content, Style},
+    common::{AppTimeFormat, Content, Notification, Style},
     widgets::pomodoro::Mode as PomodoroMode,
 };
 use color_eyre::eyre::Result;
@@ -12,6 +12,7 @@ use std::time::Duration;
 pub struct AppStorage {
     pub content: Content,
     pub show_menu: bool,
+    pub notification: Notification,
     pub app_time_format: AppTimeFormat,
     pub style: Style,
     pub with_decis: bool,
@@ -38,6 +39,7 @@ impl Default for AppStorage {
         AppStorage {
             content: Content::default(),
             show_menu: true,
+            notification: Notification::Off,
             app_time_format: AppTimeFormat::default(),
             style: Style::default(),
             with_decis: false,