Adding reference to plot_metrics and save_metrics in the fine tuning …

…section of the readme

README.md

@@ -112,6 +112,8 @@ All the parameters in the examples and recipes below need to be further tuned to
 
 * Make sure to set the right path to the model in the [training config](src/llama_recipes/configs/training.py).
 
+* To save the loss and perplexity metrics for evaluation, enable this by passing `--save_metrics` to the finetuning script. The file can be plotted using the [plot_metrics.py](./examples/plot_metrics.py) script, `python examples/plot_metrics.py --file_path path/to/metrics.json`
+
 ### Single GPU:
 
 ```bash