Export/Import single translation

In our case I want to only export single languages and not the whole entity with all translations. I want this as I export different revisions for each translation.

There are minor changes in the module needed to make this possible.

Also on import the check shouldn't be $entity->isTranslatable(), it should be $entity->getEntityType()->isTranslatable(). isTranslatable from the entity returns the config of cores content translation, where you can disabled/enable the UI for translation, while entity type isTranslatable shows if the entity supports translation. When importing even if the translation UI is disabled the translations can be imported.