Updated the Inference script

Updated the inference script to add usage examples.

inference.py

@@ -1,5 +1,10 @@
 #!/usr/bin/env python3
+"""
 
+python inference.py --model-dir nllb-finetuned-de-en --input-file input.txt --src-lang eng_Latn --tgt-lang deu_Latn
+OR
+python inference.py --model-dir nllb-finetuned-de-en --input "Hello world" --src-lang eng_Latn --tgt-lang deu_Latn
+"""
 from __future__ import annotations
 
 import argparse