Fix activating browser windows on Wayland

QDesktopServices::openUrl does not have XDG activation support yet so it can't raise an existing browser window when opening URLs

Instead use KIO::OpenUrlJob, which does support that

src/urlhelper.h

@@ -0,0 +1,13 @@
+// SPDX-FileCopyrightText: 2022 Nicolas Fella <nicolas.fella@gmx.de>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QObject>
+
+class UrlHelper : public QObject
+{
+    Q_OBJECT
+public:
+    Q_INVOKABLE void openUrl(const QUrl &url);
+};