Move data parsing into a dedicated function

Actually posting the notification is now the responsibility of a private function

src/notifications/ManagerMac.cpp

@@ -0,0 +1,11 @@
+#include "Manager.h"
+
+#include <QTextDocumentFragment>
+
+#include "Utils.h"
+
+QString
+NotificationsManager::formatNotification(const QString &text)
+{
+        return utils::markdownToHtml(text);
+}