class SyntaxTree::LParen

provides a default node.
easier to create LParen nodes without any specific value, this method
another node. This means it's required at initialization time. To make it
to it if they occur in the source, oftentimes an LParen is a child of
Because some nodes keep around a ( token so that comments can be attached

def self.default
  new(value: "(", location: Location.default)
end