float_mul_bool type promote, lhs type promote to rhs type, https://github.com/PaddlePaddle/Paddle/pull/29265

support no_sync for backward; ds support accum grad

relax librispeech audio max len to 30 second

fix recipe train and avg shell

fix readme

Add doc: ds2 online and ds2 offline

add blank_id parameter

remove useless doc and put FAQ to discussions

fix the bug of sharing cell in BiGRU and BIRNN

paddle support some bool op

remove notebook

import ctcdecoder when needed

[Static model test] Add the test process for export model

ds2 offline cer 6p4287

Fix glu

Fix bug of paddling len for "def forward_chunk_by_chunk"

Fix bug of paddling len for "def forward_chunk_by_chunk"

seed all with log; and format