Update intro doc to mention fullscreen button.
Update intro doc to mention fullscreen button.

manesiotise/dreamwriter,manesiotise/dreamwriter,rtfeldman/dreamwriter,jlongster/dreamwriter,rtfeldman/dreamwriter,zztczcx/dreamwriter,ajnsit/dreamwriter,jlongster/dreamwriter,makyo/dreamwriter,makyo/dreamwriter,Softsapiens/dreamwriter,zztczcx/dreamwriter,Iced-Tea/dreamwriter,Softsapiens/dreamwriter,ajnsit/dreamwriter,Iced-Tea/dreamwriter