code: public static RubyClass getExtensionBaseClass(Ruby rubyRuntime, String processorClassName) {
          RubyModule extensionsModule = getExtensionsModule(rubyRuntime);
          return extensionsModule.getClass(processorClassName);
      }
docs: For a simple Ruby class name like "Treeprocessor" it returns the associated RubyClass
  from Asciidoctor::Extensions, e.g. Asciidoctor::Extensions::Treeprocessor
  @param rubyRuntime
  @param processorClassName
  @return The Ruby class object for the given extension class name, e.g. Asciidoctor::Extensions::TreeProcessor