code: private void addPackageJavadoc(CompilationUnit unit, String qualifiedMainType) {
      Javadoc javadoc = unit.getPackage().getJavadoc();
      if (javadoc == null) {
        return;
      }
      SourceBuilder builder = new SourceBuilder(false);
      JavadocGenerator.printDocComment(builder, javadoc);
      javadocBlocks.put(qualifiedMainType, builder.toString());
    }
docs: Collect javadoc from the package declarations to display in the header.