Implement the new fields for fixed width area.

src/parser/fixed_width_area.rs

@@ -41,7 +41,7 @@ where
     let (remaining, mut remaining_lines) =
         many0(preceded(not(exit_matcher), fixed_width_area_line_matcher))(remaining)?;
 
-    let (remaining, _trailing_ws) =
+    let (remaining, post_blank) =
         maybe_consume_trailing_whitespace_if_not_exiting(context, remaining)?;
     let source = get_consumed(input, remaining);
     let mut value = Vec::with_capacity(remaining_lines.len() + 1);
@@ -66,6 +66,7 @@ where
                 affiliated_keywords,
             ),
             value,
+            post_blank: post_blank.map(Into::<&str>::into),
         },
     ))
 }