QmlJSEditor: add shortcut for Qt Quick Helper (ctrl+alt+space)

This shortcut forces the Qt Quick Helper to be shown if
available. The action is also registered in the context menu
so it is discoverable.


Reviewed-by: Christian Kamm

src/plugins/qmljseditor/qmljseditorplugin.h

@@ -89,6 +89,7 @@ public:
 
 public Q_SLOTS:
     void followSymbolUnderCursor();
+    void showContextPane();
 
 private Q_SLOTS:
     void openPreview();