move Window to composite templates

data/resources.gresource.xml

@@ -2,6 +2,7 @@
 <gresources>
   <gresource prefix="/org/gnome/Tour/">
     <file compressed="true" alias="style.css">resources/style.css</file>
+    <file compressed="true" preprocess="xml-stripblanks" alias="ui/window.ui">resources/ui/window.ui</file>
     <file compressed="true" alias="welcome.svg">resources/assets/welcome.svg</file>
     <file compressed="true" alias="overview.svg">resources/assets/overview.svg</file>
     <file compressed="true" alias="search.svg">resources/assets/search.svg</file>

data/resources/ui/window.ui

+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <template class="Window" parent="AdwApplicationWindow">
+    <property name="default-width">960</property>
+    <property name="default-height">720</property>
+    <property name="content">
+      <object class="PaginatorWidget" id="paginator" />
+    </property>
+  </template>
+</interface>

src/widgets/window.rs

@@ -12,9 +12,11 @@ mod imp {
     use crate::config;
     use adw::subclass::prelude::*;
 
-    #[derive(Debug, Default)]
+    #[derive(Debug, Default, gtk::CompositeTemplate)]
+    #[template(resource = "/org/gnome/Tour/ui/window.ui")]
     pub struct Window {
-        pub(super) paginator: PaginatorWidget,
+        #[template_child]
+        pub(super) paginator: TemplateChild<PaginatorWidget>,
     }
 
     #[glib::object_subclass]
@@ -22,11 +24,18 @@ mod imp {
         const NAME: &'static str = "Window";
         type Type = super::Window;
         type ParentType = adw::ApplicationWindow;
+
+        fn class_init(klass: &mut Self::Class) {
+            Self::bind_template(klass);
+        }
+
+        fn instance_init(obj: &glib::subclass::InitializingObject<Self>) {
+            obj.init_template();
+        }
     }
 
     impl ObjectImpl for Window {
         fn constructed(&self, widget: &Self::Type) {
-            widget.set_default_size(960, 720);
             widget.set_icon_name(Some(config::APP_ID));
 
             // Devel Profile
@@ -73,7 +82,6 @@ mod imp {
             last_page.add_css_class("last-page");
             self.paginator.add_page(last_page);
 
-            widget.set_content(Some(&self.paginator));
             self.parent_constructed(widget);
         }
     }