Use RsT syntax instead of markdown

docs/source/configuration.rst

@@ -1367,7 +1367,7 @@ use_system_emojis
 Determines whether emojis should be rendered by the user's system.
 
 Not all operating systems support (all) emojis. So alternatively you can let
-Converse render the emojis with [Twemoji](https://twemoji.twitter.com/).
+Converse render the emojis with `Twemoji <https://twemoji.twitter.com/>`_.
 
 See also `emoji_image_path`_.