Adds section on traits for subs

Author: JJ

doc/Language/traits.pod6

@@ -63,6 +63,10 @@ say don't-instantiate.imm for ^10;
 
 Uninstantiable classes can still be used via their class variables and methods, as above. However, trying to instantiate them this way: C<my $do-instantiate = don't-instantiate.new;> will yield the error C<You cannot create an instance of this type (don't-instantiate)>.
 
+=head2 Traits and routines
+
+Traits can be added to the definition of methods and routines to establish L<precedence|/functions#Precedence> and L<associativity|/language/functions#Associativity>. They act as a
+L<sub defined using C<trait_mod>|/type/Sub#Traits> which take as argument the types and names of the traits that are going to be added.
 
 =end pod