Add a test showing the footnote exit matcher is not handling multiple blank lines properly.

src/parser/footnote_definition.rs

@@ -124,4 +124,31 @@ line footnote.";
 line footnote."
         );
     }
+
+    #[test]
+    fn multiline_break() {
+        let input = "[fn:2] A multi-
+
+line footnote.
+
+
+not in the footnote.";
+        let initial_context: ContextTree<'_, '_> = ContextTree::new();
+        let document_context =
+            initial_context.with_additional_node(ContextElement::DocumentRoot(input));
+        let footnote_definition_matcher =
+            parser_with_context!(footnote_definition)(&document_context);
+        let (remaining, first_footnote_definition) =
+            footnote_definition_matcher(input).expect("Parse first footnote_definition");
+        assert_eq!(remaining, "not in the footnote.");
+        assert_eq!(
+            first_footnote_definition.source,
+            "[fn:2] A multi-
+
+line footnote.
+
+
+"
+        );
+    }
 }

toy_language.txt

@@ -33,3 +33,6 @@ foo bar
 [fn:2] A multi-
 
 line footnote.
+
+
+not in the footnote.