begin identity dialog implementation

src/app/browser/window/tab/item/identity/unsupported.rs

@@ -0,0 +1,27 @@
+mod widget;
+use widget::Widget;
+
+use gtk::prelude::IsA;
+use std::rc::Rc;
+
+pub struct Unsupported {
+    widget: Rc<Widget>,
+}
+
+impl Unsupported {
+    // Construct
+
+    /// Create new `Self`
+    pub fn new() -> Self {
+        Self {
+            widget: Rc::new(Widget::new()),
+        }
+    }
+
+    // Actions
+
+    /// Show dialog for given parent
+    pub fn present(&self, parent: Option<&impl IsA<gtk::Widget>>) {
+        self.widget.present(parent)
+    }
+}