use libadwaita for app & app window

src/app/browser/window/header/tray/tab.rs

@@ -0,0 +1,30 @@
+use gtk::{gio::SimpleAction, prelude::ActionExt, prelude::ButtonExt, Button};
+use std::sync::Arc;
+
+pub struct Tab {
+    pub gobject: Button,
+}
+
+impl Tab {
+    // Construct
+    pub fn new(action_tab_append: Arc<SimpleAction>) -> Self {
+        // Init widget
+        let gobject = Button::builder()
+            .icon_name("tab-new-symbolic")
+            .tooltip_text("New tab")
+            .build();
+
+        // Init events
+        gobject.connect_clicked(move |_| {
+            action_tab_append.activate(None);
+        });
+
+        // Return activated struct
+        Self { gobject }
+    }
+
+    // Getters
+    pub fn gobject(&self) -> &Button {
+        &self.gobject
+    }
+}