Re-implement LM rescore for online transducer (#1231)

Co-authored-by: Martins Kronis <martins.kuznecovs@tilde.lv>

sherpa-onnx/python/sherpa_onnx/online_recognizer.py

@@ -64,6 +64,7 @@ class OnlineRecognizer(object):
         bpe_vocab: str = "",
         lm: str = "",
         lm_scale: float = 0.1,
+        lm_shallow_fusion: bool = True,
         temperature_scale: float = 2.0,
         debug: bool = False,
         rule_fsts: str = "",
@@ -274,6 +275,7 @@ class OnlineRecognizer(object):
         lm_config = OnlineLMConfig(
             model=lm,
             scale=lm_scale,
+            shallow_fusion=lm_shallow_fusion,
         )
 
         recognizer_config = OnlineRecognizerConfig(