Link to smart match operator in the docs.

The smart match operator ~~ is linked to the design document for a better
explaination. While this is surely correct, I believe that in a "nutshell"
the user should be redirected to the official explaination of the ~~
mechanics and method ACCEPTS.

Author: fluca1978

doc/Language/5to6-nutshell.pod6

@@ -608,7 +608,7 @@ type of its arguments.
 
 While the operator has not changed, the rules for what exactly is matched
 depends on the types of both arguments, and those rules are far from
-identical in Perl 5 and Perl 6. See
+identical in Perl 5 and Perl 6. See L<~~|/routine/~~> and
 L<S03/Smart matching|https://design.perl6.org/S03.html#Smart_matching>
 
 =head2 C<& | ^> String Bitwise ops