use HTML anchors for config parameters

this avoids incorrect rendering on the man pages, since `lowdown`
neither parses the anchor syntax nor HTML.

this should rather be fixed in lowdown, as adding more anchors
would otherwise produce ever more noise and error-prone repetition.

doc/manual/generate-options.nix

@@ -9,7 +9,7 @@ let
     let
       inherit (optionsInfo.${name}) description documentDefault defaultValue aliases;
       result = squash ''
-          - [`${name}`]{#conf-${name}}
+          - <span id="conf-${name}">[`${name}`](#conf-${name})</span>
 
           ${indent "  " body}
         '';