Document the .are method (#4069)

* Document the .are method

Co-authored-by: Coke <will@coleda.com>

Author: lizmat

doc/Type/Any.pod6

@@ -781,6 +781,24 @@ Instead of throwing away the first C<$n> elements, it throws away everything
 I<but> the elements indicated by the WhateverCode, in this case all but the last
 one.
 
+=head2 method are
+
+Defined as:
+
+    multi method are()
+
+Returns the strictest type (or role) to which B<all> elements of the list
+will smartmatch.  Returns C<Nil> on an empty list.
+
+    say (1,2,3).are;        # OUTPUT: «(Int)␤»
+    say <a b c>.are;        # OUTPUT: «(Str)␤»
+    say <42 666>.are;       # OUTPUT: «(IntStr)␤»
+    say (42,666e0).are;     # OUTPUT: «(Real)␤»
+    say (42,i).are;         # OUTPUT: «(Numeric)␤»
+    say ("a",42,3.14).are;  # OUTPUT: «(Cool)␤»
+
+Available as of release 2022.02 of the Rakudo compiler.
+
 =head2 method prepend
 
 Defined as: