feature: add underline to renderer

renderer/fifty_ohm_html_renderer.py

@@ -12,4 +12,7 @@ class FiftyOhmHtmlRenderer(HtmlRenderer):
         return None
 
     def render_quote(self, token):
-        return f"„{self.render_inner(token)}“"
+        return f"„{self.render_inner(token)}“"
+
+    def render_underline(self, token):
+        return f"<u>{self.render_inner(token)}</u>"

renderer/underline.py

@@ -0,0 +1,11 @@
+import re
+
+from mistletoe.span_token import SpanToken
+
+
+class Underline(SpanToken):
+    """
+    Underline span token (<u>Untersrich</u>).
+    Identifies underlined text.
+    """
+    pattern = re.compile(r'<u>(.+)</u>')