fix(latex-renderer): thematic break on new line

Preceed `\hrulefill` by an empty line, so the thematic break is rendered
as a separate horizontal line between blocks of text. Otherwise, the
last line of the preceeding paragraph is filled with a horizontal rule.
(Tested with pdflatex, version pdfTeX 3.141592653-2.6-1.40.25 (TeX Live
2023/Debian))

mistletoe/latex_renderer.py

@@ -158,7 +158,7 @@ def render_table_cell(self, token):
 
     @staticmethod
     def render_thematic_break(token):
-        return '\\hrulefill\n'
+        return '\n\\hrulefill\n'
 
     @staticmethod
     def render_line_break(token):

test/test_latex_renderer.py

@@ -120,7 +120,7 @@ def test_table_cell(self):
         self._test_token('TableCell', 'inner')
 
     def test_thematic_break(self):
-        self._test_token('ThematicBreak', '\\hrulefill\n')
+        self._test_token('ThematicBreak', '\n\\hrulefill\n')
 
     def test_line_break(self):
         self._test_token('LineBreak', '\\newline\n', soft=False)