Standardize on the children name instead of contents.

src/parser/plain_list.rs

@@ -71,7 +71,7 @@ pub fn plain_list_item<'r, 's>(
                     source,
                     indentation: indent_level,
                     bullet: bull,
-                    contents: Vec::new(),
+                    children: Vec::new(),
                 },
             ));
         }
@@ -86,7 +86,7 @@ pub fn plain_list_item<'r, 's>(
                     source,
                     indentation: indent_level,
                     bullet: bull,
-                    contents,
+                    children: contents,
                 },
             ));
         }