Add newline behind document title

src/changelist/_format.py

@@ -50,6 +50,7 @@ def iter_lines(self) -> Iterable[str]:
             repo_name=self.repo_name, version=self.version
         )
         yield from self._format_section_title(title, level=1)
+        yield "\n"
         yield from self._format_intro()
         for title, pull_requests in self._prs_by_section.items():
             yield from self._format_pr_section(title, pull_requests)