Project: survey
Task (challenging): Add questions contents (class 'contents', file 'common/Contents.js' used by 'common/SurveyDesign.js' and 'common/SurveyPreview.js') panel fixed at the right side of the page. Contents can not cover any question content. Each contents item (class 'contents-item') has the text from the associated question's title. Click each contents item to scroll page to the associated question. Update contents after questions updated in the form. Insert after the target contents item when dragging the source one into the target one; Change the position of associated questions at the same time.