Librarian Bot: Add base_model information to model

This pull request aims to enrich the metadata of your model by adding [`facebook/mbart-large-50`](https://huggingface.co./facebook/mbart-large-50) as a `base_model` field, situated in the `YAML` block of your model's `README.md`.

How did we find this information? We performed a regular expression match on your `README.md` file to determine the connection.

**Why add this?** Enhancing your model's metadata in this way:
- **Boosts Discoverability** - It becomes straightforward to trace the relationships between various models on the Hugging Face Hub.
- **Highlights Impact** - It showcases the contributions and influences different models have within the community.

For a hands-on example of how such metadata can play a pivotal role in mapping model connections, take a look at [librarian-bots/base_model_explorer](https://huggingface.co./spaces/librarian-bots/base_model_explorer).

This PR comes courtesy of [Librarian Bot](https://huggingface.co./librarian-bot). If you have any feedback, queries, or need assistance, please don't hesitate to reach out to [@davanstrien](https://huggingface.co./davanstrien). Your input is invaluable to us!

README.md

@@ -7,6 +7,7 @@ tags:
 - generated_from_trainer
 datasets:
 - pn_summary
+base_model: facebook/mbart-large-50
 model-index:
 - name: mbart-finetuned-fa
   results: []