* add stats about duration and padding proportion
* add for utt_duration
* add stats for other recipes
* add stats for other 2 recipes
* modify doc
* minor change
* init files
* use average value as memory vector for each chunk
* change tail padding length from right_context_length to chunk_length
* correct the files, ln -> cp
* fix bug in conv_emformer_transducer_stateless2/emformer.py
* fix doc in conv_emformer_transducer_stateless/emformer.py
* refactor init states for stream
* modify .flake8
* fix bug about memory mask when memory_size==0
* add @torch.jit.export for init_states function
* update RESULTS.md
* minor change
* update README.md
* modify doc
* replace torch.div() with <<
* fix bug, >> -> <<
* use i&i-1 to judge if it is a power of 2
* minor fix
* fix error in RESULTS.md
