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/args.rs

@@ -1,5 +1,5 @@
 use crate::{
-    common::{Content, Style},
+    common::{Content, Notification, Style},
     duration,
 };
 use clap::Parser;
@@ -23,7 +23,7 @@ pub struct Args {
     )]
     pub pause: Option<Duration>,
 
-    #[arg(long, short = 'd', help = "Whether to show deciseconds or not.")]
+    #[arg(long, short = 'd', help = "Show deciseconds.")]
     pub decis: bool,
 
     #[arg(long, short = 'm', value_enum, help = "Mode to start with.")]
@@ -32,9 +32,17 @@ pub struct Args {
     #[arg(long, short = 's', value_enum, help = "Style to display time with.")]
     pub style: Option<Style>,
 
-    #[arg(long, value_enum, help = "Whether to open the menu or not.")]
+    #[arg(long, value_enum, help = "Open the menu.")]
     pub menu: bool,
 
-    #[arg(long, short = 'r', help = "Reset stored values to default.")]
+    #[arg(long, short = 'r', help = "Reset stored values to default values.")]
     pub reset: bool,
+
+    #[arg(
+        long,
+        short,
+        value_enum,
+        help = "Toggle desktop notifications on or off. Experimental."
+    )]
+    pub notification: Option<Notification>,
 }