Add a formatter

tests/formatting/out.blp

@@ -0,0 +1,28 @@
+using Gtk 4.0;
+using Adw 1;
+
+Overlay {
+  Label label {
+    label: _("'Hello World!' \"\n\t\"");
+  }
+
+  [overlay]
+  Button {
+    notify::icon-name => $on_icon_name_changed(label) swapped;
+
+    styles [
+      "destructive"
+    ]
+  }
+
+  visible: bind $isVisible(label.visible, my-menu) as <bool>;
+  width-request: bind label.width-request no-sync-create;
+}
+
+menu my-menu {
+  item (_("Label"), "action-name", "icon-name")
+
+  item {
+    action: "win.format";
+  }
+}