QmlJSEditor: refines textmarker logic

The textmarker is now updated when the document
gets updated and the textmarker is shown again,
if the user closes the QuickToolBar.

src/plugins/qmljseditor/qmljseditor.h

@@ -244,6 +244,7 @@ private slots:
     void updateOutlineNow();
     void updateOutlineIndexNow();
     void updateCursorPositionNow();
+    void showTextMarker();
     void updateFileName();
 
     void updateUses();