Generate URL fragments for index entries according to new schema

Prior to this, URI fragments rendered were aligned with the format
Documentable expected to follow, however it was recently changed
to address number of issues such as:

- Absence of special characters escaping in the fragments
- Relying on the formatting code parts that should be flexible
  in long term

lib/Pod/To/HTML.pm6

@@ -195,20 +195,17 @@ monitor Node::To::HTML {
             }
 
             when 'X' {
-                multi sub recurse-until-str(Str:D $s) { $s }
-                multi sub recurse-until-str(Pod::Block $n) { $n.contents>>.&recurse-until-str().join }
-
-                my $index-text = recurse-until-str($node).join;
                 my @indices = $node.meta;
-                my $index-name-attr =
-                        qq[index-entry{ @indices ?? '-' !! '' }{ @indices.join('-') }{ $index-text ?? '-' !! '' }$index-text]
-                        .subst('_', '__', :g).subst(' ', '_', :g);
-                $index-name-attr = $!renderer.url($index-name-attr).subst(/^\//, '');
+                # meta is by default a list of lists, so take the first element
+                # and then take `foo` part of `X<Text?|Category,foo>`.
+                my $index-entry-text = @indices[0][1];
+                my $fragment = uri-escape("index-entry-$index-entry-text");
+                $fragment = $!renderer.url($fragment).subst(/^\//, '');
                 my $text = self.node2inline($node.contents);
                 $!renderer.crossrefs{$_} = $text for @indices;
 
-                return qq[<a name="$index-name-attr"><span class="index-entry">$text\</span></a>] if $text;
-                return qq[<a name="$index-name-attr"></a>];
+                return qq[<a id="$fragment"><span class="index-entry">$text\</span></a>] if $text;
+                return qq[<a id="$fragment"></a>];
             }
 
             # Stuff I haven't figured out yet