Fix date parsing issue for org mode plugin

This patch fixes the date parsing issue currently when an entry like
`todo +d 22 01 2022` is used. I have added tests too which demonstrate
the current issue so that we can prevent future regression.

XMonad/Util/Parser.hs

@@ -52,6 +52,7 @@ module XMonad.Util.Parser (
   endBy1,
   munch,
   munch1,
+  pfail
 ) where
 
 import XMonad.Prelude
@@ -136,6 +137,10 @@ instance Alternative Parser where
 runParser :: Parser a -> String -> Maybe a
 runParser (Parser p) = fmap fst . listToMaybe . ReadP.readP_to_S p
 
+-- | Always fails
+pfail :: Parser a
+pfail = Parser $ ReadP.pfail
+
 -- | Consume and return the next character.  Fails if there is no input
 -- left.
 get :: Parser Char