Create function focus_file_text

This function focuses the text field when saving a file
It is called when the save file dialogue is opened

scene/gui/file_dialog.h

@@ -113,6 +113,8 @@ private:
 	void update_file_list();
 	void update_filters();
 
+	void _focus_file_text();
+
 	void _tree_multi_selected(Object *p_object, int p_cell, bool p_selected);
 	void _tree_selected();