Get smartmatch into index

Fixes #1587

Author: zoffixznet

doc/Language/operators.pod6

@@ -1627,6 +1627,7 @@ also modify the other.
 
 =head2 infix C«~~»
 
+X<|smartmatch operator>
 The X<smart-match operator>. Aliases the left-hand side to C<$_>, then evaluates
 the right-hand side, and calls C<.ACCEPTS($_)> on it. The semantics are left
 to the type of the right-hand side operand.