Support canceling file transfer from pseudo job

Allows to click cancel on the job popup rather than only from
within NeoChat.

src/filetransferpseudojob.h

@@ -15,6 +15,7 @@
  */
 class FileTransferPseudoJob : public KJob
 {
+    Q_OBJECT
 public:
     enum Operation {
         Download,
@@ -48,6 +49,12 @@ public:
      */
     void start() override;
 
+protected:
+    bool doKill() override;
+
+Q_SIGNALS:
+    void cancelRequested(const QString &id);
+
 private:
     QString m_path;
     QString m_eventId;