code: public static Container leftShift(Container self, Component c) {
          self.add(c);
          return self;
      }
docs: Overloads the left shift operator to provide an easy way to add
  components to a Container.
  
  @param self a Container
  @param c    a Component to be added to the container.
  @return same container, after the value was added to it.
  @since 1.6.4