Add Language Model Decoder

Closes #142 (closed)

Taking over from !222 (closed)

dan/ocr/decoder.py

@@ -597,8 +597,8 @@ class CTCLanguageDecoder:
     ) -> Dict[str, List[Union[str, float]]]:
         """
         Decode a feature vector using n-gram language modelling.
-        :param features: Feature vector of size (batch_size, n_tokens, n_frames).
-        :param batch_sizes: Prediction length of size batch_size.
+        :param batch_features: Feature vector of size (batch_size, n_tokens, n_frames).
+        :param batch_frames: Prediction length of size batch_size.
         :return: A dictionary containing the hypotheses and their confidences.
         """
         # Reshape from (batch_size, n_tokens, n_frames) to (batch_size, n_frames, n_tokens)