public <T> Builder addObjectFormatter(Class<T> objectClass,
                                          ObjectFormatter<? super T> objectFormatter) {
      if (objectFormatters == null) {
        objectFormatters = new HashMap<>(DefaultsFactory.builtinObjectFormatters());
      }
      objectFormatters.put(objectClass, objectFormatter);
      return this;
    }
Add a {@link ObjectFormatter} for specific class of object.

@param objectClass     the class of object
@param objectFormatter the object formatter to add
@param <T>             the type of object
@return the builder
@since 1.1.0
xlog/src/main/java/com/elvishew/xlog/LogConfiguration.java