mark formats that are NYI

Author: tbrowder

doc/Language/pod.pod6

@@ -52,8 +52,8 @@ Perl6-ish option pairs. That is, any of:
  Boolean (false)   :!key                 :key(False)
  String            :key<str>             :key('str')      :key("str")
  Number            :key(23)              :key(4.6)
- List              :key[1, 'b', 3]
- Hash              :key{a=>1, b=>'x'}
+ List              :key[1, 'b', 3]       # not yet implemented
+ Hash              :key{a=>1, b=>'x'}    # not yet implemented
 =end table
 
 All option keys and values must, of course, be constants since Pod is a