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/models/publicroomlistmodel.h

@@ -48,6 +48,11 @@ class PublicRoomListModel : public QAbstractListModel
      */
     Q_PROPERTY(bool hasMore READ hasMore NOTIFY hasMoreChanged)
 
+    /**
+     * @biref Whether the model is still loading.
+     */
+    Q_PROPERTY(bool loading READ loading NOTIFY loadingChanged)
+
 public:
     /**
      * @brief Defines the model roles.
@@ -98,6 +103,8 @@ public:
 
     [[nodiscard]] bool hasMore() const;
 
+    [[nodiscard]] bool loading() const;
+
     /**
      * @brief Load the next set of rooms.
      *
@@ -111,6 +118,7 @@ private:
     QString m_keyword;
 
     bool attempted = false;
+    bool m_loading = false;
     QString nextBatch;
 
     QVector<Quotient::PublicRoomsChunk> rooms;
@@ -122,4 +130,5 @@ Q_SIGNALS:
     void serverChanged();
     void keywordChanged();
     void hasMoreChanged();
+    void loadingChanged();
 };