feat(browser): support display subfolders

dataitems/folderitem.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <QJsonObject>
+#include <QStandardItem>
+#include <QQmlEngine>
+
+class FolderItem : public QStandardItem
+{
+    Q_GADGET
+public:
+    enum Roles {
+        IdRole = Qt::UserRole + 1,
+        FirstComicHashRole,
+        PathRole,
+    };
+    Q_ENUM(Roles)
+
+    explicit FolderItem(QJsonObject jsonObj, const QString &name);
+    static QHash<int, QByteArray> roleNames();
+};