code: public Map<String, String> indexDataMap(final DocWorkUnit workUnit) {
          Map<String, String> propertyMap = new HashMap<>();
          propertyMap.put("name", workUnit.getName());
          propertyMap.put("summary", workUnit.getSummary());
          propertyMap.put("filename", workUnit.getTargetFileName());
          propertyMap.put("group", workUnit.getGroupName());
  
          // Note that these properties are inserted into the toplevel FreeMarker map for the WorkUnit typed
          // as Strings with values "true" or "false", but here the same entries are typed as Booleans in the
          // in the index.
          propertyMap.put("beta", Boolean.toString(workUnit.isBetaFeature()));
          propertyMap.put("experimental", Boolean.toString(workUnit.isExperimentalFeature()));
  
          return propertyMap;
      }
docs: Return a String -> String map suitable for FreeMarker to create an index to this WorkUnit
  
  @return