Open url using QDesktopServices from Qml

This fixes some weirdness on some platforms, where Qt.openUrlExternally
does weird stuff.

resources/qml/MatrixText.qml

@@ -16,7 +16,7 @@ TextEdit {
 			timelineManager.setHistoryView(match[1])
 			chat.positionViewAtIndex(chat.model.idToIndex(match[2]), ListView.Contain)
 		}
-		else Qt.openUrlExternally(link)
+		else timelineManager.openLink(link)
 	}
 	MouseArea
 	{

src/timeline/TimelineViewManager.cpp

@@ -1,5 +1,6 @@
 #include "TimelineViewManager.h"
 
+#include <QDesktopServices>
 #include <QMetaType>
 #include <QPalette>
 #include <QQmlContext>
@@ -219,6 +220,12 @@ TimelineViewManager::openImageOverlay(QString mxcUrl, QString eventId) const
         });
 }
 
+void
+TimelineViewManager::openLink(QString link) const
+{
+        QDesktopServices::openUrl(link);
+}
+
 void
 TimelineViewManager::updateReadReceipts(const QString &room_id,
                                         const std::vector<QString> &event_ids)

src/timeline/TimelineViewManager.h

@@ -47,6 +47,8 @@ public:
         Q_INVOKABLE QString userPresence(QString id) const;
         Q_INVOKABLE QString userStatus(QString id) const;
 
+        Q_INVOKABLE void openLink(QString link) const;
+
 signals:
         void clearRoomMessageCount(QString roomid);
         void updateRoomsLastMessage(QString roomid, const DescInfo &info);