feat: start tinkering with adding a footer for the playerbar on the ApplicationWindow

desktop/qml/PlayerBar/PlayerBar.qml

@@ -0,0 +1,23 @@
+import QtQuick.Controls as Controls
+import QtQuick.Layouts
+import org.kde.kirigami as Kirigami
+
+ColumnLayout {
+    id: playerBar
+
+    Layout.fillWidth: true
+
+    Controls.Slider {
+        id: seekSlider
+
+        Layout.fillWidth: true
+    }
+    RowLayout {
+        Layout.fillWidth: true
+
+        Controls.Button {
+            icon.height: Kirigami.Units.iconSizes.small
+            icon.name: "media-seek-backward"
+        }
+    }
+}