Adds Cool.printf, refs #2277

doc/Type/Cool.pod6

@@ -1480,13 +1480,28 @@ the case it's being used as a C<sub>
     say 1.unpolar(⅓*pi);
     # OUTPUT: «0.5000000000000001+0.8660254037844386i␤»
 
+=head2 routine printf
 
-=begin comment
+Defined as:
+
+     method printf (*@args)
+     multi sub printf(Cool:D $format, *@args)
+
+As a method, takes the object as a format using
+L<the same language as C<Str.sprintf>|/type/Str#routine_sprintf>; as a sub, its
+first argument will be
+the format string, and the rest of the arguments will be substituted in the
+format following the format conventions.
 
+    "%s is %s".printf("þor", "mighty");# OUTPUT: «þor is mighty»
+    printf( "%s is %s", "þor", "mighty"); # OUTPUT: «þor is mighty»
+
+
+=begin comment
 
 
 TODO:
-sprintf, printf
+sprintf
 
 =end comment