Auto model for conditional generation
# 🚀 Feature request

The majority of tasks (CausalLM, QuestionAnswering...) have the option to be loaded without importing the specific architecture of the model with `AutoModel` yet for  `ConditionalGeneration`  you need to import the specific class.

is there a technical reason restraining such an implementation?

If you can confirm that this would be a good plus, I can push my modification for this.<|||||>Hello! These models are available in `AutoModelForSeq2SeqLM`!<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.