Make the explore page search loading process more obvious

Adds progress bars, lots of them! Now it's easier to tell if NeoChat is
trying it's best to load the public room list.

src/qml/Page/JoinRoomPage.qml

@@ -7,7 +7,7 @@ import QtQuick.Controls 2.15 as QQC2
 import QtQuick.Layouts 1.15
 import Qt.labs.qmlmodels 1.0
 
-import org.kde.kirigami 2.15 as Kirigami
+import org.kde.kirigami 2.19 as Kirigami
 import org.kde.kirigamiaddons.labs.components 1.0 as KirigamiComponents
 
 import org.kde.neochat 1.0
@@ -255,5 +255,25 @@ Kirigami.ScrollablePage {
                 }
             }
         }
+
+        footer: RowLayout {
+            width: parent.width
+
+            QQC2.ProgressBar {
+                visible: publicRoomsListView.model.loading && publicRoomsListView.count !== 0
+                indeterminate: true
+                padding: Kirigami.Units.largeSpacing * 2
+                Layout.alignment: Qt.AlignHCenter | Qt.AlignVCenter
+                Layout.topMargin: Kirigami.Units.largeSpacing
+                Layout.bottomMargin: Kirigami.Units.largeSpacing
+                Layout.leftMargin: Kirigami.Units.largeSpacing
+                Layout.rightMargin: Kirigami.Units.largeSpacing
+            }
+        }
+
+        Kirigami.LoadingPlaceholder {
+            anchors.centerIn: parent
+            visible: publicRoomsListView.model.loading && publicRoomsListView.count === 0
+        }
     }
 }