Fix "attachemnt" typo

Author: mattaudesse

mime-mail/Network/Mail/Mime.hs

@@ -146,7 +146,7 @@ type Alternatives = [Part]
 data Part = Part
     { partType :: Text -- ^ content type
     , partEncoding :: Encoding
-    -- | The filename for this part, if it is to be sent with an attachemnt
+    -- | The filename for this part, if it is to be sent with an attachment
     -- disposition.
     , partDisposition :: Disposition
     , partHeaders :: Headers