Fix username regex, add media endpoint

src/formatters.nim

@@ -8,7 +8,7 @@ from unicode import Rune, `$`
 const
   urlRegex = re"((https?|ftp)://(-\.)?([^\s/?\.#]+\.?)+(/[^\s\)]*)?)"
   emailRegex = re"([a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+)"
-  usernameRegex = re"(^|[^\S]|\.|>)@([A-z0-9_]+)"
+  usernameRegex = re"(^|[\s\.,>])@([A-z0-9_]+)"
   picRegex = re"pic.twitter.com/[^ ]+"
   cardRegex = re"(https?://)?cards.twitter.com/[^ ]+"
   ellipsisRegex = re" ?…"