Print character offset from rust's parse perspective during compare.

src/parser/object.rs

@@ -374,3 +374,9 @@ impl<'s> Source<'s> for Timestamp<'s> {
         self.source
     }
 }
+
+impl<'s> Source<'s> for PlainText<'s> {
+    fn get_source(&'s self) -> &'s str {
+        self.source
+    }
+}