Add Clapper usage as GTK widget

examples/widget-example.js

@@ -0,0 +1,40 @@
+imports.gi.versions.Gtk = '4.0';
+
+const Gtk = imports.gi.Gtk;
+const Clapper = imports.clapper;
+
+let app = new Gtk.Application({
+    application_id: 'com.clapper.WidgetExample'
+});
+
+app.connect('activate', () => {
+    let window = new Gtk.ApplicationWindow({
+        application: app,
+        title: 'Clapper Widget Example',
+    });
+    let box = new Gtk.Box({
+        orientation: Gtk.Orientation.VERTICAL,
+    });
+    let label = new Gtk.Label({
+        label: [
+            'Clapper is used as a widget and placed below.',
+            'Double click it to enter fullscreen!',
+        ].join('\n')
+    });
+    let widget = new Clapper.Widget();
+
+    widget.connect('fullscreen-changed', (widget, isFullscreen) => {
+        label.set_visible(!isFullscreen);
+    });
+    window.connect('show', () => {
+        let media = 'http://distribution.bbb3d.renderfarming.net/video/mp4/bbb_sunflower_1080p_30fps_normal.mp4';
+        widget.player.set_media(media);
+    });
+
+    box.append(label);
+    box.append(widget);
+
+    window.set_child(box);
+    window.present();
+});
+app.run([]);