Make sure to escape backslash's in .js search files

It was not escaping backslashes, so when a backslash appeared right
before the ending " double quote mark, it ruined the syntax for the rest
of the javascript file. This should hopefully get the search working
again on docs.perl6.org

Author: samcv

htmlify.p6

@@ -762,7 +762,7 @@ sub write-search-file() {
             .pairs.sort({.key}).map: -> (:key($name), :value(@docs)) {
                 qq[[\{ category: "{
                     ( @docs > 1 ?? $kind !! @docs.[0].subkinds[0] ).wordcase
-                }", value: "$name", url: "{rewrite-url(@docs.[0].url).subst('"', '\"', :g)}" \}]] #"
+                }", value: "$name", url: " {rewrite-url(@docs.[0].url).subst(｢\｣, ｢\\｣, :g).subst('"', '\"', :g) }" \}]] #"
             }
     }).flat;