Returns true if this points to the start of the paragraph delimiter characters for a line.
Delimiters will be either a newline, a carriage return, a carriage return followed by a newline, or a Unicode paragraph separator character.
Note that an iterator pointing to the \n of a \r\n pair will not be counted as the end of a line, the line ends before the \r. The end iterator is considered to be at the end of a line, even though there are no paragraph delimiter chars there.
whether this is at the end of a line