docs: add callbacks example

examples/callbacks.rs

@@ -0,0 +1,36 @@
+use glib::MainLoop;
+use libnotify_rs::{
+    functions::{init, uninit},
+    notification::Notification,
+};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    init("Coffee reminder")?;
+    let mut notify = Notification::new("Drink coffee", "Click me when you're done drinking", None)?;
+
+    // We need to have  a glib main loop in order to receive callback actions
+    let main_loop = MainLoop::new(None, false);
+    let loop_clone = main_loop.clone();
+
+    notify.add_action("default", "I'm drinking!", move |action_name| {
+        println!("User drunk his coffee!");
+        println!("Action was named: {}", action_name);
+        loop_clone.quit();
+    })?;
+
+    notify.show()?;
+
+    main_loop.run();
+
+    // Thanks to the main loop we can also read why the notification was closed
+    println!(
+        "Notification closed, because: {:?}",
+        notify.get_closed_reason()
+    );
+
+    println!("Glib mainloop has ended");
+
+    uninit();
+
+    Ok(())
+}