Add documetation for get_emoji_regex

Author: alexmick

docs/index.rst

@@ -9,7 +9,7 @@ Module documentation
 --------------------
 
 .. automodule:: emoji_data_python
-    :members: unified_to_char, replace_colons, all_doublebyte, find_by_shortname, find_by_name
+    :members: unified_to_char, replace_colons, all_doublebyte, find_by_shortname, find_by_name, get_emoji_regex
 
     .. attribute:: emoji_data