Document \qq[] escape in q quoting docs

Author: zoffixznet

doc/Language/quoting.pod6

@@ -117,6 +117,15 @@ There are no backslashes here, only lots of $$$!
 No $interpolation {here}!
 Just a literal "\n" here
 
+The C<\qq[...]> escape sequence enables
+L«C<qq> interpolation|/language/quoting#Interpolation:_qq» for a portion
+of the string. Using this escape sequence is handy when you have HTML markup
+in your strings, to avoid interpretation of angle brackets as hash keys:
+
+    my $var = 'foo';
+    say '<code>$var</code> is <var>\qq[$var.uc()]</var>';
+    # OUTPUT: «<code>$var</code> is <var>FOO</var>␤»
+
 =head2 X<Interpolation: qq|quote,qq;quote," ">
 
 =begin code :allow<B L> :skip-test